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 Post subject: Tricky maths question
PostPosted: Thu Sep 08, 2011 11:22 pm 
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Joined: Sat Jun 12, 2010 7:21 pm
Posts: 21
Can someone help me with these questions please:

1) Halim grows a sunflower which he measures each week. After eight weeks it is 1.32m tall and in the next week it growa a further 19am.
How many more centimetres must it grow to be 2m tall (1 mark) Answer is 49cms or (0.49m)

2) A 4x4x4 cube is made of 1cm cubes. The outside of the large cube is painted red.
How many of the 1cm cubes will have exactly 2 sides painted red, Answer is 24

3) John is three times older than his sister Mary. In three years time he will be twice as old as Mary. How old is John now? Answer is 9 years. I know it looks simple but my brain is not functioning at the moment.

Many Thanks.


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PostPosted: Fri Sep 09, 2011 7:09 am 
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Joined: Wed Feb 27, 2008 8:59 am
Posts: 2001
Quote:
1) Halim grows a sunflower which he measures each week. After eight weeks it is 1.32m tall and in the next week it growa a further 19cm.
How many more centimetres must it grow to be 2m tall (1 mark) Answer is 49cms or (0.49m)


1.32m = 132cm & 2m=200cm
how much it will grow all together
132+19= 151cm
(how much it needs to grow to reach 2m
200-151=49cm or 0.49m

Quote:
2) A 4x4x4 cube is made of 1cm cubes. The outside of the large cube is painted red.
How many of the 1cm cubes will have exactly 2 sides painted red, Answer is 24


Only the middle 2 cubes on each edge of the cube have two sides painted red. There are 12 edges on the cube so 24 in total. This is much easier if you can see the cube.
Image

Quote:
3) John is three times older than his sister Mary. In three years time he will be twice as old as Mary. How old is John now? Answer is 9 years.


The ages of the children are related, at the present they are 3:1 and in three years time they are 2:1

For the present work in multiples of 3 - 3,6,9,12,15
In three years time multiples of 2 - 2,4,6,8,10,12,14

The first common multiple is 12. So in 3 years time John will be 12 and Mary 6
So at the present time John is 12-3=9 years old


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PostPosted: Fri Sep 16, 2011 3:48 pm 
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Joined: Sat Jun 12, 2010 7:21 pm
Posts: 21
Many Thanks Mitasol. :)


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