11 Plus Exams Forum

We have come across a few of these questions: Eg. a grid of 32 squares has 20 shaded. What is the percentage of shaded squares?
The answers are all very close, so guestimating isn't an option. Is the only way to do the long division of 20/32?
That would take me a few minutes to complete with a pencil, never mind my DS in an exam!

Hi

I'm no expert but i would do this by :

20/32 simplify to 5/8
1/8 as a % is 12.5
5/8 = 12.5 x 5 = 62.5%

I'm sure there may be a better way to do this and someone more able will come and help.

Fm, yoyo......where are you?

mm2

Hi mm2

seems a sensible way to do it!!!

It is worth kids knowing what the equivalent percentage of common fractions (other than 1/2 and 1/4!) is:
eg 1/8 =12.5%
1/6 = 16.6%
1/3 = 33.3%
1/12 = 8.3%

Thanks for that. He hasn't done much percentage work at school so it's all down to me. That tip should be very helpful.
Thanks

Hi Haze

The maths revision aids are good.

http://www.elevenplusexams.co.uk/pdf/Ma ... _Aid_2.pdf

ooo even better Mitasol - thanks for pointing that out...

we try calculating percentage etc when cutting pies up. even better calculate in terms of radians - cos then you can have so many Pi(e) radians..

And this is with 10 and 11 year old childeren? I didn't touch radians until maths A level!!!

can't you just do, 10% of 32 would be 3.2, therefore 20% would be 6.4??

Haze wrote:And this is with 10 and 11 year old childeren? I didn't touch radians until maths A level!!!

nah just messing about eating pizzas and pies at home... they know how to ask for a portion in radians... wouldn't be able to do owt else with them yet

Milla wrote:can't you just do, 10% of 32 would be 3.2, therefore 20% would be 6.4??

don't think that works ...

10% of 32 = 32/10 - you are trying to calculate 20/32