Page 34 - 新思维数学活动用书9 样章

2.6 Deriving and using formulae

9 Kimma buys and sells furniture. She uses the formula in the box to work out the percentage
profit she makes.
Work out the percentage profit Kimma makes on each piece of furniture.
a cost price = $28, selling price = $42
−
b cost price = $150, selling price = $162 percentage profit = selling price cost price ×100
cost price
c cost price = $35, selling price = $73.50
10 In many countries, the distance of a horse race is measured in furlongs (F ) and yards (Y ).
A formula to convert furlongs and yards into metres (m) is shown in the box.

m is the number of metres
+
m = 220 FY where: F is the number of furlongs
.
109
Y is the number of yards
Work out the distance, in metres, of each horse race.

Give each answer correct to the nearest metre.
a 2 furlongs and 50 yards b 6 furlongs and 100 yards
c 5 furlongs and 75 yards d 8 furlongs

11 Make x the subject of each formula. Write if A, B or C is the correct answer.

+
−
y
a y = 5x + k A x = yk B x = yk C x =− k
5 5 5
x
b y =−2 ab A x = 3 y + 2 ab B x = 3( y + 2 ab) C x = 3 y − 2 ab
3
+
c y = gx A x = ky − g B x = k(y − g) C x = ky + g
k

d y = 3 x −5 p A x = 2( y −5 p) B x = 2 y +5 p C x = 2( y + 5 p)
2 3 3 3
12 Make n the subject of each formula.

+
n
a p = 3n − 8 b q =+ k c p = rn d h = 5 n − 2
7 2 w r 2

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