Grade Seven Answers


1)

Answer:

     Let D = the weight of one duck
         d = the weight of one duckling

Solve:     (3D + 2d = 32)*3 ------>  9D + 6d = 96               

           (4D + 3d = 44)*2 ------>  8D + 6d = 88
                                    ______________
                                     
                                     1D + 0d = 8 -----> D = 8

        Substitute to solve for d:
 
                4D + 3d = 44
              4(8) + 3d = 44
                32 + 3d = 44
                     3d = 12
                      d = 4                     

        Thus,   

                2D + d = 2(8) + 4 = 20 kgs.

2)

Answer:

     Let x = rate of one man = 23 m3/ 1 day = 8m3/day
        3x = rate of three men = 3(8m3/day) = 24m3/day

     Volume to be shoveled = 64m3

        Therefore, it would take three men  
                             64m3/(24m3/day) = 2 2/3 days

3)

Answer:

     Let x = total number of bags

        5(1/2 x) + 2 (1/2 x) = 252
                   2.5x + 1x = 252
                        3.5x = 252
                           x = 72 bags.

4)

Answer:

        Let x = number of seats in Theatre 3
           T1 = Theatre 1 = 270 seats
           T2 = Theatre 2 = 150 + x

               T1 + T2 + T3 = 800 seats
        270 + (150 + x) + x = 800
                   420 + 2x = 800
                          x = 190

     If there are x = 190 seats in theatre 3, then 

        Theatre 2 has 
                150 + 190 = 340 seats

5)

Answer:

        If the price of 5 Kg of flour in 1969 = $0.75, then 
        
                1970 = $0.75 x 1.15 = $0.8625

                1971 = ($0.75 x 1.15) x .95
                     = $0.82

6)

Answer: 

     l x h x w = 60 
     h(5)(4) = 60
     h = 3

     A(1) = 4 x 5 = 20
     2A(2) = 2(3)(5) = 30
     2A(3) = 2(3)(4) = 24
     4A(4) = 4(3)(3) = 36

     Total A = A(1) + 2A(2) + 2A(3) + 4A(4)
             = 20 + 30 + 24 + 36
             = 110cm2

7)

Answer:

     Let x = price of lipstick
     Let 1/2 x = price of shampoo


     Cost of lipstick AND shampoo, combined = x + 1/2 x

     Money spent on lipstick AND shampoo combined:
                
                $50.00 - ($15.00)*2 = $20.00
        
        Therefore, 
                x + 1/2 x = $20.00
                     1.5x = $20.00
                        x = $13.33
        
                Lipstick cost:      x = $13.33
                Shampoo cost:   1/2 x = 1/2 * $13.33 = $6.67

8)

Answer:

        Let x = Stephanie's contribution.

        $30.00 + $10.00 = $40.00
     
        $40.00 + x = $54.99     
                 x = $14.99

9)

Answer:

     e = 3(3)-1 = 8
     f = 1/2(3) = 1.5
     g = 3/8(3) + (3/8)(3)
       = 18/8 = 2.25

Volume (1)  = 1/2(a)(c)(b)         Volume (2)   = 1/2(a)(c)(f)
            = 1/2(3)(4)(3)                      = 1/2(3)(4)(1.5)
            = 36/2 = 18litres                   = 9 litres
               = (18)dm3                       = (9)dm3

Volume (3)  = (e)(g)(c)
            = (8)(2.25)(4)
            = 72 litres = (72)dm3

Total Volume = 18 + 9 + 72 = 99 litres = (99)dm3

Let t = time

    t = 99 x 1min/2l x 60sec/1min

      = 99 (60sec)/2l = 49.5(60sec) = 2970

10)

Answer:

     Dimensions B:
                 5/8 = 8/x
                  64 = 5x
                12.8 = x

    (a) Surface Area = 2 * Area A + 2 * Area B + Area (top) + Area (bottom)     
                     = 2(8*5) + 2(8*12.8) + 2(5*12.8)
                     = 412.8  
                
    (b) Volume = l x w x h
                   = (12.8)(5)(8)
                   = 512

11)

Answer:

     2r + 3L + 3w + 3pi*a  = 2(10) + 3(100) + 3(20) + 3pi(20)
                           = 568.50m

     (2r+L) + 2L + 3W + 3piW = (2(10)+40) + 2(40) + 3(20) 3pi(20)
     = 388.50 m

12)

Answer:

    75% full = 75% * 1000 horses
                  = 750 horses

    If there are 200 ponies, there must be (750 - 200) = 550 quarter horses

13)

Answer:

        Let x = width of chalkboard

        Therefore, 
           3x = length of chalkboard 


    Since sides of square are equal, 
                3x - 3 = x + 3
                    2x = 6
                     x = 3

    Dimensions of chalkboard:

        width  =  x = 3 meters wide
        length = 3x = 9 meters long

14)

Answer:

     3 x 152km/month x 12 months/year = 5472 km/year.

15)

Answer:

     (700.00)(5/6)(4/5) = $466.67

16)

Answer:

               

        4 triangles

17)

Answer:

     a)  225 * 8 litres + 515 * 27 litres = Total Volume
                             15705 litres = 15.705 kilolitres

     b)  [(150*8 + 5*27) / 15705] x 100 percent = 8.500 percent.

18)

Answer:

        Cost of first kilometer = $0.30
        Total cost of additional kilometers = (3.20 - 0.30) 
                                            = 2.90

          Total number of kilometers = 1 + ($2.90/$0.05) 
                                     = 1 + 58
                                     = 59 km

19)

Answer:

                 SHAWN                          RACHEL

start         0.05 litres     = 0.05          0.05 litres   = 0.05
moving       8km * (1L/22km)  = 0.36        9km * (1L/20km) = 0.45
stopped    2min * (0.16L/min) = 0.32              0         =   0
                                ____                          ____
TOTAL                           0.73 L                        0.50 L

                    Therefore, Shawn used more gas

20)

Answer:

    Total area of square = (1/4 + 3/4) * (2/3 + 1/3)
                   = 1 * 1
                   = 1

    Shaded area = (2/3 * 3/4) = 0.5

        Fraction of Total area shaded = 0.5/1 
                                      = 50%

21)

Answer:

     Let x = the number of hours that had already passed
     1/4 x = the number of hours remaining
   
     IF total number of hours in a day = 40, THEN
                x + 1/4x = 40
                    5/4x = 40
                    160x = 5 
                       x = 160/5 
                       x = 32

     Hours remaining = 1/4 x
                     = 1/4(32)
                     = 8

22)

Answer:

     Volume  = l * w * h
             = (20)(30)(40)cm3
             = 24000cm3

     New height = initial h + 0.3h
                = 1.3h
                = 1.3 * 40cm
                = 52 cm
        
     IF height = 52 cm, solve for w:     
        
        Volume = l * w * h 
    24000 cm3 = (20cm)(w)(52cm)
    24000 cm3 = 1040(w)cm2
             w = 23.08 cm

23)

Answer:

   Pattern:    
       16 - 13 = 3         10 - 7 = 3
       10 - 9 = 1          8 - 7 = 1

        3 barks for 1 car
      
  Therefore, 22 barks for 12 cars.

24)

Answer:


25)

Answer:

   Let x = price for each big rig tire
        

           Size         Price/tire 

          0.75m     $100/4 = $25.00 each

          1.5m              x


Solve for x:

   0.75m/$25.00 = 1.5/x 
          
          0.75x = 1.5 * $25.00
     
          0.75x = $37.50

              x = $50.00/tire

Therefore:

          Price for 18 tires = 18($50.00) = $900.00

26)

Answer:

1)

                                   Cost of Pizza = $20.00

                                   PROPORTIONS: 
                                   Jane: 5/20 = 1/4
                                   Mike: 8/20 = 4/10 = 2/5
                                   Mary: 3/20
                                   Joe:  4/20 = 1/5


2)

                                   Jane: 5/20 = 1/4
                                   Mike: 8/20-4/20 = 4/20 = 1/5
                                   Mary: 3/20 + 4/20 = 7/20
                                   Joe:  4/20 = 1/5

27)

Answer:

     Let x = the number of cookies eaten on the first day

                    Cookies Eaten

     Day 1                x
         2              x + 1(6)        
         3              x + 2(6)           
         4              x + 3(6)             
         5              x + 4(6)             

     TOTAL            5x + 10(6) = 100 cookies
     
        Solve for x:
                      5x + 10(6) = 100
                         5x + 60 = 100
                              5x = 40
                               x = 8

28)

Answer:

   Since s = sides of square

        Area square = s^2
        
        Area triangle = (1/2)b*h
                      = (1/2)(1/2 s)(1/2 s) 
                      = 1/8 s^2

    Ratio = Area triangle/Area square = 1/8

29)

Answer:

     Time to connect two chains = 1 cut + 1 weld        
                                = 10s + 25s

     To connect all chains together = 5 connections
                                    = 5(10+25)s 
                                    = 5(35) 
                                    = 175

30)

Answer:

               

31)

Answer:

    Let x = artist's scale    

    1)  Convert meters (m) to centimeters (cm)

        In reality, rose bush = .75m * 100 cm/m = 750 cm

        
    2)  Solve for x

        1.5x = 750                      
           x = 750/1.5 
           x = 500 cm
        
    IF artist's scale = 1 cm:500cm THEN

        In reality, house = 7.5cm * 500 cm 
                          = 3750 cm
                          = 3.75 m

32)

Answer:

    When 3 lines are extended from vertex, opposite side is divided 
    into four sections

    When 3 lines are extended from two vertices: 
    Number of nonoverlapping sections formed = 42 = 16

    If 4 lines are extended from vertex, opposite side is divided into 
    five sections
 
    Therefore, when 4 lines are extended from two vertices:
    Number of nonoverlapping sections formed = 52 = 25

33)

Answer:

     Let x = total number of points for the season
        
        1653 points were scored by ST. F.X., but ST. F.X. had only 38 
        percent of the total points for all four teams.  
     

        Solve for x:

             x= 1653/0.38 = 4350 points

        ACADIA:

          14% * 4350 = 609 

        DALHOUSIE:

          Acadia + 50 = 609 + 50 = 659

        SMU:

          4350 - (1653 + 609 + 659) = 1429

34)

Answer:

        Total area of quadrilateral = x * y

        A1 = A2 = A3 = A4       

    Solve:

        A1 = 1/2 (b * h)        b = 1/2 x
                                h = 1/2 y

           = 1/2 (1/2 x * 1/2 y)
           = 1/8 xy

        Since A1 = A2 = A3, 
                
                A1 + A2 + A3 = 1/8 xy + 1/8 xy + 1/8 xy
                             = 3/8 xy   

        Since total area of quadrilateral = x * y = xy, 

                3/8 of total area of quadrilateral is shaded by triangles 
                        A1, A2, and A3

35)

Answer:

        Rachel:
                WEEKLY: $5.15/hr * 13 hrs/wk = $66.95/wk
                YEARLY: $66.95/wk * 52 weeks = $3481.40/yr
                
        Stephanie:
                WEEKLY: $5.15/hr * 20 hrs/wk = $103/wk
                YEARLY: $103 * 52 weeks = $5356/yr
        
IF Stephanie and Rachel make the same amount of money in one year, THEN
        Stephanie must only work:

                ($3481.40/yr)/($103/wk) = 33.8 weeks    

        Therefore, she must take 
                52 - 33.8 = 18.2 weeks/yr Unpaid Vacation Time

36)

Answer:

a)

                                          p = 2(6 + 210) + 2(6+460)
                                          = 432 + 932
                                          = 1364m

b)
Area of paved path = 2*3*466 + 2*3*210 = 4056 m2


37)

Answer:

        Let x = amount covered

        DAY       Amount Covered

         16              x
         15             1/2 x
         14             1/4 x

Therefore, on Day 14, 1/4 of the petri dish was covered with bacteria

38)

Answer:

        Amount of change Joe receives:
                        $2.00 - $1.08 = $0.92

        Two possible variations of coins received:

           (i)  3 quarters, 3 nickels, 2 pennies

                3(.25) + 3(.05) + 2(.01) = .92

          (ii)  2 quarters, 4 dimes, 2 pennies

                2(.25) + 4(.10) + 2(0.01) = .92

39)

Answer:

Equation for y1:

       y1 = m1 x + b            m1 = (12-0)/(9-0)
                                   = 4/3
    y1 = 4/3 x + b

Since y1 passes through origin, 0 = b
     
       y1 = 4/3 x + 0
       y1 = 4/3 x               

Equation for y2:

       y2 = m2 x + b         m2 = (0-12)/(16-0)
                                = -3/4

       y2 = -3/4 x + b

y2 passes crosses y-axis at (0,12), therefore b = 12

     y2 = -3/4 x + 12     

Since m1 = negative reciprocal of m2,

        y1 is perpendicular to y2

40)

Answer:

Water lost per second:

     3 * (1 1/3 mL) =  4mL

Number of seconds in one year:

  60s/min x 60 min/hr x 24hr/day x 365d/y = 31 536 000 s

Water lost in one year = 4mL/s * 31 536 000 s
                       = 126 144 000 mL

Convert to Litres:

        126 144 000mL * 1L/1000 mL = 126 144 litres

41)

Answer:

        Area of circle = pi * r2
        
        Side of square = 2 * r = 2r
        Area of square = (2r)2 = 4r2

Area of shaded region = Area of square - 4 * (1/4 area of each circle) 
                      = 4r2 - 4 * 1/4(pi * r2) 
                      = 4r2 - pi r2 
                      = (4 - pi)r2

42)

Answer:

PURCHASE PRICE:
        Rachel:   5/6 * $5600.00 = $4666.67
        Raelene:  4/5 * $4666.67 = $3733.33
        Rick:     3/4 * $3733.33 = $2800.00


OR you can take a shortcut:

Rick paid:
     $5600.00 (5/6)(4/5)(3/4) = $2800.00

43)

Answer:

    Travel time from A to C = 12:45 -11:00 = 1 hr 45 min = 1.75 hr

        Distance travelled:
                D = Rate * Time
                  = 3 km/hr * 1.75 hr
                  = 5.25 km
        
        Distance remaining (from point C to B):
                  = (12 - 5.25) km
                  = 6.75km

    Time remaining = 2:00 - 12:45 = 1 hr 15 min = 1.25 hr

        Rate at which distance must be travelled:
                Rate = Distance/Time
                     = 6.75 km / 1.25 hr
                     = 5.4 km/hr

44)

Answer:

     AO = BO = CO = DO = EO = 5

     Therefore, we have 5 isosceles triangles.  The altitude of an
     isosceles triangle intersects the side with which it makes
     the 90 degree angle.


               

     h of each triangle = square root of 5^2-3^2
                        = 4.05

     Aera = 5 (1/2)(4.05)(5.88)
          = 59.54

45)

Answer:

     Area of semicircle = 1/2 pi r2         r = 3
     Area of Trapezoid  = 1/2(AD)(AB+CD)

     Total Area  = 1/2 pi (9) + 1/2(6)(12+8)
                 = 74.137 cm2

46)

Answer:

     360 degrees = 120 degrees + 90 degrees + C + (2/3 * C)
             360 = 210 + 5/3 * C
             150 = 5/3C
             450 = 5C
           450/5 = C  
              90 = C

Substitute:
        If C = 90 degrees, Then
           D = 2/3 * 90 = 60 degrees

47)

Answer:

     The four sides of EFGH are equal

     Find length of one side:

        To find HG:
                (HC)2 + (CG)2 = (HG)2
        Square root (32 + 12) = HG
               Square root (10) = HG

     Since four sides are equal,

        Area of EFGH = (square root 10)2 = 10

48)

Answer:

    Each revolution of B meets 24 teeth of A
        Therefore, (36 - 24) = 12 teeth of wheel A are not 
        met with the first revolution of B

    Since 12/24 = 1/2

        Wheel B must turn 1 1/2 times for every revolution of A

49)

Answer:

     
Triangle BAC similar Triangle EFC       Triangle DCA similar Triangle EFA

Therefore,

           30/h = 40/(40 - b)                     20/h = 40/b
      1200 - 30b = 40h                   
                             Substitute
     1200 - 30b = 20b  <--------------------        40h = 20b

     1200 - 30b = 20b                                 h = 1/2 b
           1200 = 50b      
        1200/50 = b           Substitute                     
          24m = b    --------------------->         h = 1/2 (24m)
                                                     h = 12 m