Page 32 - 新思维数学学生用书8 样章

2.1 Constructing expressions

Think like a mathematician

7 In pairs or in a small group, discuss.
Sofia, Zara and Arun discuss what to write for this problem.

‘I think of a number, n. I divide by 3, then multiply by 2.’

I think the
expression
2n
is .
3
If you divide by 3
I think the then times by 2, you
expression is are finding of the
2
3
n × 2. number, so you can
3
2
write n.
What do you think? 3
Make a conjecture and convince the other members of your group.

8 a Sort these cards into groups of equivalent expressions.

A 3 × x B x + 3 C 4 x D 4 × x E 3 × x
4 4 3 3 4

F 3 x G 3 + x H 3x I 4x J 3 + x
4 4 4 3 4
b Which card is in a group on its own?

9 This is part of Pedro’s classwork. Question
Are Pedro’s answers correct? If not, write the Write an expression for these.
correct answers for him. a one-third of x add 4
b 5 subtract two-fifths of y

Answers

a x + 4 b 2y − 5
3 5

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