# Estimating a Calculation – use it when you don’t want an exact answer Estimation is used when you want a rough or approximate idea for the answer to a.

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Estimating a Calculation – use it when you don’t want an exact answer Estimation is used when you want a rough or approximate idea for the answer to a sum

First step is to round all the numbers in the sum Nearest ten? Nearest hundred? Nearest thousand? Nearest ten thousand? Nearest ten pence Nearest one pound or even smaller

How to round You need to identify each place value in the number

Place value in our system ThousandsHundredsTensOnes or units 3456 How would you read this number?

Place value in our system ThousandsHundredsTensOnes or units 3456 Three thousand four hundred fifty six

Place value in our system ThousandsHundredsTensOnes or units 8012 How would you read this number?

Place value in our system ThousandsHundredsTensOnes or units 8012 eight thousand twelve There are no hundreds

Place value in money signtensonesten pence one pence £20.12 Twenty pounds and twenty pence There is no ‘p’ here

Place value in money ten pence one pence 43p Forty three pence There is no ‘£’ here

How to round Now that you have identified each place value, you need to identify the halfway point

The halfway point between forty and fifty 4050 What value is the halfway point? 45 Forty five is the halfway point?

The halfway point between one hundred and two hundred 100200 What value is the halfway point? 150 One hundred fifty is the halfway point?

The halfway point between eight and nine thousand 8000 9000 What value is the halfway point? 8500 Eight thousand five hundred is the halfway point?

The halfway point between seven thousand five hundred and seven thousand six hundred 75007600 What value is the halfway point? 7550 Seven thousand five hundred fifty is the halfway point?

The halfway point between twenty and thirty pence 20 pence30 pence What value is the halfway point? 25p Twenty five pence is the halfway point?

What is halfway between these two sets of numbers? 30 and 40 100 and 200 700 and 800 1000 and 1100 1500 and 1600 2000 and 3000 130 and 140 0 and 1 35 150 750 1050 1550 2500 135 0.5 Did you notice that there is a five in each of these numbers?

How to round Now that you’ve identified each place value and the halfway point - you have to decide in which half of the line your number is in

In which half of the line ? 50 pence60 pence Round 52 pence to the nearest 10 pence. Is 52 pence closer to 50 pence or 60 pence? 55 This half Or this half?

In which half of the line ? 30 pence40 pence Round each of these to the nearest 10p 35 This half Or this half? 34p37p31p36p35p

In which half of the line ? £3£4 Round each of these to the nearest £1 £3.50 This half Or this half? £3.34£3.72£3.05£3.90£3.50

In which half of the line ? £40£50 Round each of these to the nearest £10 £45 This half Or this half? £43.34£48.72£44.05£43.50£49.05

Rounding to the nearest 10 without a number line 283 the answer is either 280 or 290 if it is a 5, 6, 7, 8 or 9 round up Round to 10 underline the tens place Look at the digit to the right to decide if it is a 0, 1, 2, 3 or 4 round down

Rounding to the nearest 10 without a number line 8 the answer is either 0 or 0 if it is a 5, 6, 7, 8 or 9 round up Round to 10 underline the tens place Look at the digit to the right to decide if it is a 0, 1, 2, 3 or 4 round down

Rounding to the nearest 100 without a number line 455 the answer is either 400 or 500 if it is a 5, 6, 7, 8 or 9 round up Round to 100 underline the hundreds place Look at the digit to the right to decide if it is a 0, 1, 2, 3 or 4 round down

Rounding to the nearest 1 without a number line 1.8 the answer is either 1 or 2 if it is a 5, 6, 7, 8 or 9 round up Round to 1 underline the ones place Look at the digit to the right to decide if it is a 0, 1, 2, 3 or 4 round down

Rounding to the nearest 10p without a number line £0.08 the answer is either 0p or 10p if it is a 5, 6, 7, 8 or 9 round up Round to 10p underline the 10p place Look at the digit to the right to decide if it is a 0, 1, 2, 3 or 4 round down

Rounding to the nearest £1 without a number line £2.05 the answer is either £2 or £3 if it is a 5, 6, 7, 8 or 9 round up Round to £1 underline the £1 place Look at the digit to the right to decide if it is a 0, 1, 2, 3 or 4 round down

When rounding to the nearest ten – these are possible answers 0010203040 5060708090 100110120130140 150160170180190 200210220….

When rounding to the nearest 100 – these are possible answers 0100200300400 500600700800900 10001100120013001400 15001600170018001900 200021002200….

When rounding to the nearest 10 pence – these are possible answers 0p10p20p30p40p 50p60p70p80p90p £1.00£1.10£1.20£1.30£1.40 £1.50£1.60£1.70£1.80£1.90 £2.00£2.10£2.20….

When rounding to the nearest £1 – these are possible answers £0£1£2£3£4 £5£6£7£8£9 £10£11£12£13£14 £15£16£17£18£19 £20£21£22….

When rounding to the nearest £10 – these are possible answers £0£10£20£30£40 £50£60£70£80£90 £100£110£120£130£140 £150£160£170£180£190 £200£210£220….

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