Page 41 - 新思维数学学生用书7 样章

2 Expressions, formulae and equations

10 Yola uses the formula C = x + y to work out the total cost of tickets for
an adult and a child to go swimming.
a Arun considers the formula.

I think that x is the cost
of an adult ticket and y is the
cost of a child ticket.

Explain why Arun could be correct,

but also why he could be incorrect.
b How could you improve Yola’s formula to make it easier to use?
11 Mateo cuts a small piece of wire from a large piece
of wire. He works out how much wire he has
left using the formula W = p – q.
a Sofia considers the formula.

I think that p is the length of the
small piece of wire and q is the length
of the large piece of wire.

Is Sofia correct? Explain your answer.
b How could you improve Mateo’s formula to
make it easier to use? Tip

12 What value of k can you substitute into these expressions to give you Start by trying
the same answer? different values
for k.
k + 10 3k 20 − k

How well do you think you understood this section on formulae?

Summary checklist

I can substitute numbers into expressions.
I can write formulae.
I can understand and use formulae.

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