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help plzzzzzzzz gcse maths

alex spent 2/7 of his pocket money on computer games.he spent 1/4 of his pockets money on sweets. he saved the rest. given that alex saved £3.90, work out how much pocket money he got.

the answer is £8.40

right this is the question and i cant work out how to get £8.40 ... please help meeeeeeeeeeeeeeeeee
Reply 1
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2710
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Original post by moniasajid
alex spent 2/7 of his pocket money on computer games.he spent 1/4 of his pockets money on sweets. he saved the rest. given that alex saved £3.90, work out how much pocket money he got.

the answer is £8.40

right this is the question and i cant work out how to get £8.40 ... please help meeeeeeeeeeeeeeeeee


Take x to be the amount of pocket money he had originally and form an equation
First off, find a common denominator for 2/7 and 1/4. It is 28.
7*4=28, so do the same to the numerator. 2*4=8. So now your 2/7 has become 8/28.
Now do the same for the second fraction. 4*7=28. So, 1*7=7. So that fraction has become 7/28.
Right, now add them together.
8/28+7/28= 15/28. That's how much pocket money he spent overall.
So the amount left over would be 13/28, as a fraction.
We know 13/28 is £3.90, because it's been given. Now divide £3.90 by 13= 30p. So, 1/28= 30p.
Now multiply 30p by the denominator, 28 to get 30*28= 840.
Put that into the right format and you get £8.40!


~We live in an age of smart phones and stupid people.
Reply 3
Avatar for moniasajid
moniasajid
OP
1
Original post by Meliss
First off, find a common denominator for 2/7 and 1/4. It is 28.
7*4=28, so do the same to the numerator. 2*4=8. So now your 2/7 has become 8/28.
Now do the same for the second fraction. 4*7=28. So, 1*7=7. So that fraction has become 7/28.
Right, now add them together.
8/28+7/28= 15/28. That's how much pocket money he spent overall.
So the amount left over would be 13/28, as a fraction.
We know 13/28 is £3.90, because it's been given. Now divide £3.90 by 13= 30p. So, 1/28= 30p.
Now multiply 30p by the denominator, 28 to get 30*28= 840.
Put that into the right format and you get £8.40!


~We live in an age of smart phones and stupid people.


aw thank you so much ......
Original post by moniasajid
aw thank you so much ......


:biggrin:
Anything else you need help with?


~We live in an age of smart phones and stupid people.
(edited 11 years ago)

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