Page 22 - 新思维数学活动用书7 样章

2.1 Constructing expressions

9 Match each description (a to f ) to the correct expression (i to vii).
Description Expression

a Multiply x by 5 and add 4. i 4x + 5

b Multiply x by 4 and add 5. ii 4x − 5
c Multiply x by 5 and subtract 4. iii 4 − 5x
d Multiply x by 5 and subtract from 4. iv 5 − 4x

e Multiply x by 4 and subtract 5. v 5x − 4
f Multiply x by 4 and subtract from 5. vi 5 − 5x

vii 5x + 4

Marcus writes this description for the expression that did not have a match:

Multiply x by 5 then subtract 5.

Is Marcus correct? Explain your answer.
10 Write an expression for each of these situations.
You can choose your own letters, but make sure you write what your

letters represent.
a The total cost of seven drinks and six bags of potato chips.
b The total value of three rings is doubled.

Challenge
11 Write an expression for each of these descriptions.
a k more than g b h less than t

c y more than eight times x d three times a multiplied by b
12 Write a description for each of these expressions.
a v + 7u b 8w − d
c 5x + 3y d 7pq

Tip

Remember the correct order of operations. Multiplication comes
before addition and subtraction.

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