Page 20 - 新思维数学活动用书7 样章

2.1 Constructing expressions

d This bag has apples.

e This bag has apples. Tip

2 Two balls are added to each of these bags. Write down the In part c choose
missing numbers. your own letter

a There is one ball in the bag. for the number
Add two balls, so there are now 1 + 2 = balls of balls; for
in the bag. example, b.

b There are balls in the bag. You cannot work
Add two balls, so there are now + 2 = out b + 2,
balls in the bag. so just leave
c There are balls in the bag. the expression
Add two balls, so there are now +2 balls in as it is.

the bag.
3 A bag has n counters in it.
Match the statement in each rectangle to its correct expression in Tip

the ovals. The first one has been done for you: A and iv. An expression is
a statement that
I add three I add one I add six I add nine I add seven
counters to counter to counters to counters to counters to contains letters
the bag. the bag. the bag. the bag. the bag. and sometimes
A B C D E
numbers; for
n + 7 n + 6 n + 1 n + 3 n + 9 example, n + 7.
i ii iii iv v

4 Sofia has a box that contains t toys. Write an expression for the total
number of toys she has in the box when: Tip
a she puts in four more toys In each part of
b she takes out two toys the question
c she adds five toys Sofia starts with

d she takes out half of the toys. t toys.

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