Page 20 - 新思维数学活动用书9 样章

2.2 Constructing expressions

12 The graph shows the amount it costs to hire a bicycle.
Cost to hire a bicycle
80
70

60
50
Cost in $ 40

30
20

10
0
0 1 2 3 4 5 6
Number of days

a How much does it cost to hire a bicycle for
i 1 day ii 3 days?
b How much extra is it per day to hire a bicycle? Tip
c There is a standard hire charge, before the amount per day is In part c, look at

added on. How much is this charge? the charge for
d Write an expression for the total cost to hire a bicycle for d days. 0 days.
13 The diagram shows a rectangle.
The lengths of the sides of the rectangle are written as expressions.

a 2 + 3a
2

2b(b – 4b – 3)
2
a Show that when a = 4 and b = 5 the rectangle is in fact a square.
b Use your answer to part a to work out the perimeter of the square when a = 4 and b = 5.
c Write an expression for the perimeter of the square above
i in terms of a only

ii in terms of b only.
Write each expression in its simplest form. Tip
d Use the expressions in part c to work out the perimeter of the

square when a = 4 and b = 5. In part c i, use
2
Are your answers to parts b and d the same? If not, check only the a 2 + 3 a
your working. side length.

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