Page 15 - 新思维数学活动用书8 样章

2 Expressions, formulae and equations

Practice

6 Shen thinks of a number, n.
Write an expression for the number Shen gets when he
a multiplies the number by 7 then adds 4

b divides the number by 6 then subtracts 8
c adds 4 to the number then divides by 5
d subtracts 4 from the number then divides by 5.
7 a Sort these cards into groups of equivalent expressions.

7 × x x − 7 7 7 + x x
A B C x + D E × 7
8 8 8 8 8

F 7 × x G 7x H 7 + x I x + 7 J 7 x
8 8 8 8 8

b Which card is on its own?
8 This is part of Kim’s homework.

Question
Write an expression for

a one-fifth of x add 7 b six subtract two-thirds of y
Answers
x + 7 2y
a b 6 –
5 3

Are Kim’s answers correct? If not, write the correct answers.
9 a Write an expression for
i one-quarter of x add 5

ii three-fifths of x subtract two
iii one add one-half of x
iv eleven subtract five-sixths of x.
b Describe in words each of these expressions.

i x − 9 ii 2x + 10 iii 25 − 2x iv 12 + 7x
2 3 9 10

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