estimating a calculation – use it when you don’t want an exact answer
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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? - PowerPoint PPT PresentationTRANSCRIPT
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
Place value in our system
Thousands
Hundreds
Tens Ones or units
3 4 5 6
How would you read this number?
Place value in our system
Thousands
Hundreds
Tens Ones or units
3 4 5 6
Three thousand four hundred fifty six
Place value in our system
Thousands
Hundreds
Tens Ones or units
8 0 1 2
How would you read this number?
Place value in our system
Thousands
Hundreds
Tens Ones or units
8 0 1 2
eight thousand twelveThere are no
hundreds
Place value in money
sign tens
ones
ten pence
one pence
£ 2 0 . 1 2
Twenty pounds and twenty pence
There is no ‘p’ here
The halfway point between forty and fifty
40 50
What value is the halfway point?
45
Forty five is the halfway point?
The halfway point between one hundred and two hundred
100 200
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
7500 7600
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 pence 30 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 pence 60 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 pence 40 pence
Round each of these to the nearest 10p
35 This half
Or this half?
34p 37p 31p 36p 35p
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
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
0p 10p 20p 30p 40p
50p 60p 70p 80p 90p
£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 …. ….