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| You are in : Numbers / | |
| Mental addition and subtraction |
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| 1: | You and your friend go swimming. Your friend swims 150 metres and
you swim 400 metres. How much further did you swim?
You said: 250
That's right! The correct answer is 400 metres - 150 metres = 250 metres. The correct answer is 500
metres - 150 metres = 250 metres.
You said: 200
Not quite - you're 50 metres short. The correct answer is 400 metres - 150 metres = 250 metres. You said: 550
No, I think you've added the two distances together. The correct answer is 400 metres - 150 metres = 250 metres. You said: 250 That's the right number but you need to say that it's 250 metres. The correct answer is 400 metres - 150 metres = 250 metres. |
| 2: | What is 32 + 101 + 199?
You said: 332
That's right! The correct answer is 32 + 101 + 199 = 332. The correct answer is 32
+ 101 + 199 = 332.
You said: 232
No, you've missed out a hundred. The correct answer is 32 + 101 + 199 = 332. You could have tried rounding down 101 to 100, rounding up 199 to 200 and then adding 32. You said: 331
Not quite - just one out! You could try counting on from 20. The correct answer is 332. You said: 333 Not quite - just one out! The correct answer is 32 + 101 + 199 = 332. Did you think of rounding down 101 to 100, rounding up 99 to 100 and then adding 32? |
| 3: | Breakfast cereal is £1.06 for own label and £2.99 for a brand name.
What could you save by buying the cheaper cereal?
You said: £1.93
That's right. To find how much you will save, the sum is £2.99 - £1.06 = £1.93. To find how much you will
save the sum is £2.99 - £1.06 = £1.93.
You said: £1.83
Not quite - you're just out by 10p. To find how much you will save, the sum is £2.99 - £1.06 = £1.93. To work out the sum you could have tried counting on from £1.06. You said: £2.05
Oops - you just needed to take the cost of the own label breakfast cereal from the cost of the brand name one. To find how much you will save the sum is £2.99 - £1.06 = £1.93. You could try counting on from £1.06. You said: £1.06 No, that's just the price of the cheaper cereal. You needed to take the cost of the own label cereal from the cost of the brand name one. To find how much you will save the sum is £2.99 - £1.06 = £1.93. You could have tried counting on from £1.06. |
| 4: | Long life milk is 27p for a one pint carton. What would be the cost
of buying 2 cartons?
You said: 54p
Well done! The correct answer is 27p + 27p = 54p. The correct answer is 27p
+ 27p = 54p
You said: 44p
You've lost 10p somewhere. The correct answer is 27p + 27p = 54p. You could try 30p + 30p then take 6 from the answer. You said: 52p
Not quite - the correct answer is 27p + 27p = 54p. You could try 30p + 30p then take 6 from the answer. You said: 57p You're out by just 3p - the correct answer is 27p + 27p = 54p. You could try 30p + 30p then take 6 from the answer. |
| 5: | You want to go to a theme park for a day. One is 44 kilometres from
where you live and another is 107 kilometres away. What is the difference
between the two distances?
You said: 63 kilometres
Yes, that's right! The correct answer is 107 kilometres - 44 kilometres = 63 kilometres The correct answer is 107
kilometres - 44 kilometres = 63 kilometres.
You said: 151 kilometres
No, I think you've added instead of subtracting. The correct answer is 107 kilometres - 44 kilometres = 63 kilometres. You said: 53 kilometres
Oops - you've missed 10 kilometres somewhere. The correct answer is 107 kilometres - 44 kilometres = 63 kilometres. You said: 62 kilometres Nearly - you're just one out. The correct answer is 107 kilometres - 44 kilometres = 63 kilometres. |
| 6: | What is 1 002 - 401?
You said: 601
Yes - the correct answer is 1 002 - 401 = 601. Did you say 1 000 - 400 = 600 and 2 - 1 = 1 and then add together 600 and 1? The correct answer is 1 002
- 401 = 601. Did you say 1 000 - 400 = 600, and 2 - 1 = 1,
then add together 600 and 1?
You said: 1403
Oops - you've added instead of subtracting. The correct answer is 1 002 - 401 = 601. You could have tried 1 000 - 400 = 600 and 2 - 1 = 1, then added together 600 and 1. You said: 603
Not quite - you're just two out. The correct answer is 1002 - 401 = 601. Did you think of saying 1 000 - 400 = 600, and 2 - 1 = 1, then adding together 600 and 1? You said: 600 Not quite - you're just one out. The correct answer is 1 002 - 401 = 601. Did you think of saying 1 000 - 400 = 600, and 2 - 1 = 1, then adding together 600 and 1? |
| 7: | You're buying three tins of food for a friend's cat. One tin weighs
250g and the other two weigh 330g each. What is the total weight of
the three tins?
You said: 910g
That's right. The correct answer is 250g + 330g + 330g = 910g. The correct answer is 250g
+ 330g + 330g = 910g.
You said: 580g
You've only added the weight of two of the tins. The correct answer is 250g + 330g + 330g = 910g. You said: 900g
Nearly - you're 10g out. The correct answer is 250g + 330g + 330g = 910g. You said: 900g No, you've missed 100g somewhere. The correct answer is 250g + 330g + 330g = 910g. |
| 8: | A packet of biscuits costs 39p. What would be the cost for 2 packets?
You said: 78p
Yes, well done. The correct answer is 39p + 39p = 78p. The correct answer is 39p
+ 39p = 78p.
You said: 80p
Not quite - did you round 39p up to 40p and forget to take the 2p off at the end? The correct answer is 39p + 39p = 78p. You said: 68p
No, you've lost 10p somewhere. The correct answer is 39p + 39p = 78p. You said: 98p Maybe you've chosen the wrong biscuits! The correct answer is 39p + 39p = 78p. |
| 9: | What is 302 + 298?
You said: 600
Well done! The correct answer is 302 + 298 = 600. The correct answer is 302
+ 298 = 600.
You said: 604
Not quite. The correct answer is 302 + 298 = 600. Did you think of rounding down 302 by 2 to 300, and rounding up 298 by 2 to 300? You said: 700
No, that's 100 too many. The correct answer is 302 + 298 = 600. Did you think of rounding down 302 by 2 to 300, and rounding up 298 by 2 to 300? You said: 598 Not quite. The correct answer is 302 + 298 = 600. Did you think of rounding down 302 by 2 to 300 and rounding up 298 by 2 to 300? |
| 10: | Margarine is priced at £1.79 or 99p. How much would you save by buying
the cheaper margarine?
You said: 80p
You've got it right. To find how much you will save the sum is £1.79 - 99p = 80p. Would you like to have another go or try a different level? To find how much you will
save the sum is £1.79 - 99p = 80p.
Would you like to have another go or try a different level? You said: £2.78
Oops - you've added them together. To find how much you will save the sum is £1.79 - 99p = 80p. You could try counting on from 99p. Would you like to have another go or try a different level? You said: £2.79
No - to find how much you will save the sum is £1.79 - 99p = 80p. You could try counting on from 99p. Would you like to have another go or try a different level? You said: 89p Not quite, you've got the right idea, but you've added in an extra 9p. To find how much you will save, the sum is £1.79 - 99p = 80p. You could try counting on from 99p. Would you like to have another go or try a different level? |