Page 44 - MAT KS3 Y8 Cambridge CheckPoint

3.8 Estimating and approximating

✦ Exercise 3.8

In each question in this exercise:
i Work out the answer to the problem.
ii Show all your working and at each step explain what it is that you have worked out.
iii Make sure your working is clearly and neatly presented.
iv Use estimation or inverse operations to check your answer.
1 Mrs Kumal is saving money to go on holiday.
Money saved so far:
Altogether she needs to save $350.
So far she has saved these amounts. $38 $57 $22 $45 $65 $54 $24
How much more money does she need to save?

2 Jian is an electrician. For each job he does he charges $32 an hour plus a call-out fee of $35.
1
a Jian does a job for Mr Lee. It takes him 2 hours.
2
How much does he charge Mr Lee?
b Jian charges Mrs Wu a total of $171.
How long did the job for Mrs Wu take?
Give your answer in hours and minutes. Cash price
$799
3 Essian is going to buy a television.
He sees the television he wants advertised in a store.
Essian can either buy the television using cash or a Payment plan
payment plan. 1st payment: $215 then
How much more will the television cost Essian if he 8 monthly payments of $82
uses the payment plan rather than paying cash?
4 Maha is going to keep six hens. One hen, on average, will produce five eggs every week.
There are 52 weeks in one year.
Maha is going to sell all the eggs her hens produce for $1.25 for six eggs.
How much money should Maha make from selling the eggs in one year?

Summary

You should now know that: You should be able to:
★ When you multiply a number by 0.1 (or 0.01) it has ★ Read and write positive integer powers of 10.
the same effect as dividing the number by 10 ★ Multiply integers and decimals by 0.1 and 0.01.
(or 100).
★ Order decimals, including measurements.
★ When you divide a number by 0.1 (or 0.01) it has the ★
same effect as multiplying the number by 10 (or 100). Round whole numbers to the nearest 10, 100, 1000, 10
000, etc.
★ When you order decimal numbers that involve ★
measurements, you must make sure all your Round decimal numbers to the nearest whole
number or one or two decimal places.
measurements are in the same units.
★ Add and subtract integers and decimals.
★ When you multiply or divide a number by a decimal
you can use the value of the decimal to work out an ★ Divide integers and decimals by a single-digit
equivalent calculation. number to a given number of decimal places.
★ When you solve problems, make sure your work is ★ Multiply and divide integers and decimals by a
set out neatly and answers are explained so that decimal, by considering equivalent calculations.
someone else can understand what you have done. ★ Use estimation and inverse operations to check
working.

42 3 Place value, ordering and rounding