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You are in : Numbers / |
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Mental addition and subtraction |
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| 1: | Your friend has moved into a new flat and is organising a small 'housewarming'
celebration. You're going to help out with the shopping! Items costing
these amounts have already been bought. What is the exact amount already
spent? £1.00, 98p, £1.02, £1.03, 97p.
You said: £5.00
That's right - the correct answer is £1 + 98p + £1.02 + £1.03 + 97p = £5. This is one of the rare occasions when an estimate would have produced the exact answer as well! The correct answer is £1
+ 98p + £1.02 + £1.03 + 97p = £5. This is one of the rare occasions
when an estimate would have produced the exact answer as well!
You said : £4.97
Nearly right - the correct answer is £1 + 98p + £1.02 + £1.03 + 97p = £5. This is one of the rare occasions when an estimate would have produced the exact answer as well! You said : £5.05
Nearly right - the correct answer is £1 + 98p + £1.02 + £1.03 + 97p = £5. This is one of the rare occasions when an estimate would have produced the exact answer as well! You said : £4.98 Nearly right - the correct answer is £1 + 98p + £1.02 + £1.03 + 97p = £5. This is one of the rare occasions when an estimate would have produced the exact answer as well! |
| 2: | You are in the bakery section, where you choose these items. You don't
need to know the cost exactly - what would be a close estimate? Hint
- round up to the nearest 50p. Big sliced white loaf (own label) 46p,
Farmhouse brown sliced (own label) 49p, French stick 42p, Doughnuts
99p, Scones 89p
You said: £3.50
That's right. If you round to the nearest 50p you get a good estimate. 50p + 50p + 50p + £1 + £1 = £3.50. If you round to the nearest
50p you get a good estimate. 50p + 50p + 50p + £1 + £1 = £3.50.
You said: £2.50
Not quite. If you round to the nearest 50p you get a good estimate. 50p + 50p + 50p + £1 + £1 = £3.50. You said: £4.50
Not quite. If you round to the nearest 50p you get a good estimate. 50p + 50p + 50p + £1 + £1 = £3.50. You said: £4.00 Not quite. If you round to the nearest 50p you get a good estimate. 50p + 50p + 50p + £1 + £1 = £3.50. |
| 3: | Milk is priced at 93p for a 4-pint carton and £1.37 for 6 pints. How
much more does 6 pints cost?
You said: 44p
You're right. The correct answer is £1.37 - 93p = 44p. The correct answer is £1.37
- 93p = 44p.
You said: 40p
You've lost 4p somewhere. The correct answer is £1.37 - 93p = 44p.. You could try counting on from 93p. You said: 50p
If you tried estimating, you forgot to take off the odd pence. The correct answer is £1.37 - 93p = 44p. You could try counting on from 93p. You said: 43p Not quite - you're just 1p short. The correct answer is £1.37 - 93p = 44p. You could try counting on from 93p. |
| 4: | Yoghurt can cost from 44p to £1.58 for a similar size tub. What is
the price difference between these two tubs?
You said: £1.14
Yes, that's right. The correct answer is £1.58 - 44p = £1.14. The correct answer is £1.58
- 44p = £1.14.
You said: £1.22
Not quite - the correct answer is £1.58 - 44p = £1.14. You could try counting on from 44p. You said: £2.02
No, you've added the price of the two pots together instead of subtracting. The correct answer is £1.58 - 44p = £1.14. You could try counting on from 44p. You said: £1.02 Oops - be careful to subtract the smaller amount from the larger one. The correct answer is £1.58 - 44p = £1.14. You could try counting on from 44p. |
| 5: | Egg prices are 65p a box, or 82p a box for free range. How much more
would you pay for free range?
You said: 17p
You're right! The correct answer is 82p - 65p = 17p. The correct answer is 82p
- 65p = 17p.
You said: 27p
Not quite - that's 10p too much. The correct answer is 82p - 65p = 17p. You could try counting on from 65p. You said: £1.47
Oops - be careful to subtract the smaller amount from the larger one. The correct answer is 82p - 65p = 17p. You could try counting on from 65p. You said: 16p Just 1p out! The correct answer is 82p - 65p = 17p. You could try counting on from 65p. |
| 6: | Look at these prices for fish fillets. Which two prices have a difference
of 15p? a) 94p b) £1.17 c) £1.44 d) 83p e) 68p
You said: d & e
Correct! The correct answer is d & e, because 83p - 68p = 15p. The correct answer is d
& e, because 83p - 68p = 15p.
You said: a & b
Not quite - the difference between 94p and £1.17p is 23p. The correct answer is d & e, because 83p - 68p = 15p. You said: a & c
Not quite - the difference between 94p and £1.44 is 50p. The correct answer is d & e, because 83p - 68p = 15p. You said: a & d Not quite - the difference between 94p and 83p is 11p. The correct answer is d & e, because 83p - 68p = 15p. |
| 7: | 5kg bags of potatoes are priced at £1.69. What would be the cost for
2 bags at this price?
You said: £3.38
Yes, the correct answer is 2 x £1.69 = £3.38. The correct answer is 2 x
£1.69 = £3.38.
You said: £2.38
Oops - you've missed £1 out somewhere. The correct answer is £1.69 + £1.69 = £3.38. You could try £1.70 + £1.70 then take 2p from the result. You said: £3.48
Not quite - that's 10p too much. The correct answer is £1.69 + £1.69 = £3.38. You could try £1.70 + £1.70, then take 2p from the result. You said: £3.28 Not quite - you've missed 10p somewhere. The correct answer is £1.69 + £1.69 = £3.38. You could try £1.70 + £1.70, then take 2p from the result. |
| 8: | Apples are 65p a bag, oranges 75p a bag and bananas 45p. What will
be the total cost for one bag of each of these items?
You said: £1.85
Yes, that's it. The correct answer is 65p + 75p + 45p = £1.85. The correct answer is 65p
+ 75p + 45p = £1.85.
You said: £2.00
Not quite. If you were estimating, £2.00 would be a good estimate, but the correct answer is 65p + 75p + 45p = £1.85. You said: £1.95
Sorry, you're 10p over - the correct answer is 65p + 75p + 45p = £1.85. You said: £2.15 Not sure what you did here - that's 30p too much. The correct answer is 65p + 75p + 45p = £1.85. |
| 9: | Own label multi-packs of crisps cost £1.29, while brand name multi-packs
are £2.78. How much could you save by buying a cheaper pack?
You said: £1.49
Correct! To find how much you will save the sum is £2.78 - £1.29 = £1.49. To find how much you will
save the sum is £2.78 - £1.29 = £1.49.
You said: £1.50
No, you're just 1p over. To find how much you will save the sum is £2.78 - £1.29 = £1.49. You could try counting on from £1.29. You said: £1.59
Not quite - you've added in an extra 10p. To find how much you will save the sum is £2.78 - £1.29 = £1.49. You could try counting on from £1.29. You said: £1.48 No, you're just 1p under. To find how much you will save the sum is £2.78 - £1.29 = £1.49. You could try counting on from £1.29. |
| 10: | At the kiosk you treat yourself to a magazine at £1.25, a drink costing
45p and a newspaper costing 35p. What will be the total cost for these
items?
You said: £2.05
That's right! The correct answer is £1.25 + 45p + 35p = £2.05. Would you like to have another go or try a different level? The correct answer is £1.25
+ 45p + 35p = £2.05.
Would you like to have another go or try a different level? You said: £2.15
Not quite, that's 10p too much. The correct answer is £1.25 + 45p + 35p = £2.05. Would you like to have another go or try a different level? You said: £2.20
Not quite, that's 15p too much. The correct answer is £1.25 + 45p + 35p = £2.05. Would you like to have another go or try a different level? You said: £1.70 I think you forgot the newspaper! The correct answer is £1.25 + 45p + 35p = £2.05. Would you like to have another go or try a different level? |
