Page 19 - 新思维数学活动用书7 样章

2 Expressions,

formulae and

equations

2.1 Constructing expressions

Here are three bags, each with a different number of balls inside.
Key word

expression

Tip
This bag has b balls. You
This bag has This bag has cannot see how many Remember that
two balls. four balls. balls are in this bag, so the correct order
you can choose any letter of operations
to represent the number.
is used in
Exercise 2.1 algebra as well
as in number

Focus calculations.

1 Write down the missing number for each of the following. Divisions and
If you do not know the number, choose your own letter to multiplications
represent it. come before
additions and
a This box has counter. subtractions.

b This box has counters.
Tip

In part c you do
c This box has counters.
not know how
many counters

are in this box,
so choose your
own letter.

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