Page 24 - 新思维数学活动用书7 样章

2.2 Using expressions and formulae

3 Work out the value of n − 1 when: Tip
a n = 5 b n = 6 c n = 7 d n = 8
4 Work out the value of the expression in each rectangle and match it In part a,

n− 1 = 5 − 1 =
to its correct answer in the oval. The first one has been done for you:
A and iii.

y + 2 y – 2 4 + y 10 – y y + 3
when y = 3 when y = 10 when y = 2 when y = 1 when y = 0
A B C D E

8 6 5 3 9
i ii iii iv v

5 Write down ‘True’ or ‘False’ for each of these statements.
If a statement is false, work out the correct value of the expression.
The first one has been done for you.
a The value of 2m when m = 5 is 7. False; when m = 5, 2m = 10. Tips

b The value of 3m when m = 8 is 24. 2m means 2 × m,
c The value of 9p when p = 2 is 11. so 2 × 5 = 10.
w
d The value of when w = 6 is 3. w
2 2 means w ÷ 2.
x
e The value of when x = 12 is 6.
3

Practice

6 Work out the value of each expression.
a a + 10 when a = 6 b b − 3 when b = 120
c c + z when c = 3 and z = 17 d d − y when d = 40 and y = 15

e 3e when e = 20 f f when f = 35
5
g g + 2x when g = 1 and x = 6 h h − 4w when h = 17 and w = 2

i 2i + 3v when i = 3 and v = 2 j j + u when j = 30 and u = 3
2
+
k 24 − 3 when k = 8 l pq when p = 11 and q = 22
k 3

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