Estimating a Calculation use it when you dont

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 n n n Nearest ten? hundred? thousand? ten thousand? Nearest ten pence Nearest one pound or even smaller

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

Place value in our system Thousands Hundreds Tens 3 4 5 Ones or units 6 How would you read this number?

Place value in our system Thousands Hundreds Tens 3 4 5 Ones or units 6 Three thousand four hundred fifty six

Place value in our system Thousands Hundreds Tens 8 0 1 Ones or units 2 How would you read this number?

Place value in our system Thousands Hundreds Tens 8 0 1 eight thousand twelve Ones or units 2 There are no hundreds

Place value in money sign tens ones ten one pence £ 2 0. 1 2 There is no ‘p’ here Twenty pounds and twenty pence

Place value in money ten pence 4 one pence 3 p 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 40 50 45 What value is the halfway point? Forty five is the halfway point?

The halfway point between one hundred and two hundred 100 200 150 What value is the halfway point? One hundred fifty is the halfway point?

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

The halfway point between seven thousand five hundred and seven thousand six hundred 7500 7600 7550 What value is the halfway point? Seven thousand five hundred fifty is the halfway point?

The halfway point between twenty and thirty pence 20 pence 30 pence 25 p What value is the halfway point? Twenty five pence is the halfway point?

What is halfway between these two sets of numbers? n n n n 30 and 40 100 and 200 700 and 800 1000 and 1100 1500 and 1600 2000 and 3000 130 and 140 0 and 1 n n n n 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 pence i Th sh alf 60 pence Or this half ? 55 Round 52 pence to the nearest 10 pence. Is 52 pence closer to 50 pence or 60 pence?

In which half of the line ? 30 pence 40 pence Or alf sh i Th 35 this half ? Round each of these to the nearest 10 p 34 p 37 p 31 p 36 p 35 p

In which half of the line ? £ 3 £ 4 Or alf sh i Th £ 3. 50 this half ? Round each of these to the nearest £ 1 £ 3. 34 £ 3. 72 £ 3. 05 £ 3. 90 £ 3. 50

In which half of the line ? £ 40 £ 50 Or alf sh i Th £ 45 this half ? Round each of these to the nearest £ 10 £ 43. 34 £ 48. 72 £ 44. 05 £ 49. 05 £ 43. 50

Rounding to the nearest 10 without a number line 283 the answer is either 280 or 290 Round to 10 underline the tens place Look at the digit to the right to decide if it is a 5, 6, 7, 8 or 9 round up 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 Round to 10 underline the tens place Look at the digit to the right to decide if it is a 5, 6, 7, 8 or 9 round up 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 Round to 100 underline the hundreds place Look at the digit to the right to decide if it is a 5, 6, 7, 8 or 9 round up 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 Round to 1 underline the ones place Look at the digit to the right to decide if it is a 5, 6, 7, 8 or 9 round up if it is a 0, 1, 2, 3 or 4 round down

Rounding to the nearest 10 p without a number line £ 0. 08 the answer is either 0 p or 10 p Round to 10 p underline the 10 p place Look at the digit to the right to decide if it is a 5, 6, 7, 8 or 9 round up 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 Round to £ 1 underline the £ 1 place Look at the digit to the right to decide if it is a 5, 6, 7, 8 or 9 round up if it is a 0, 1, 2, 3 or 4 round down

When rounding to the nearest ten – these are possible answers 00 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 ….

When rounding to the nearest 100 – these are possible answers 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 ….

When rounding to the nearest 10 pence – these are possible answers 0 p 10 p 20 p 30 p 40 p 50 p 60 p 70 p 80 p 90 p £ 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 ….