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 Post subject: You lovely people..maths question help please??Posted: Sun Jan 11, 2015 12:56 pm

Joined: Fri Sep 19, 2014 4:32 pm
Posts: 262
question is about various numbers of discs (D), envelopes (E) and squares (S) in balance, they show pictures of scales which are in balance, so ...

A) 2D + 1E = 2S
2D + 3E = 3S

4D + 3E = ?

The top two are in perfect balance. How many squares are needed to balance the bottom set (what is ?).

I MAKE THE ANSWER 5 squares (because 2D + 2D = 4D and 1E + 3E = 4E, therefore 2S + 3S = 5s)

B) [the shapes may not weigh the same as in part (a)]

5D + 1E = 5S

3D + 2E = 4S

6E = ?

The top two scales are in perfect balance. How many squares will be needed to balance the bottom set?

NO IDEA HOW TO WORK THIS OUT!!

...Thank you

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 Post subject: Re: You lovely people..maths question help please??Posted: Sun Jan 11, 2015 1:12 pm

Joined: Thu Apr 04, 2013 10:39 am
Posts: 845
For a), is there an error in your second equation?

For b), your starting point could be 5D + 1E = 5S, so

10D + 2E = 10S

nyr

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 Post subject: Re: You lovely people..maths question help please??Posted: Sun Jan 11, 2015 1:29 pm

Joined: Mon Feb 12, 2007 1:21 pm
Posts: 14003
nyr - isn't it better to elimiate E as we're not interested in it?

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 Post subject: Re: You lovely people..maths question help please??Posted: Sun Jan 11, 2015 1:40 pm

Joined: Fri Sep 19, 2014 4:32 pm
Posts: 262
Sorry yes error - part a last equation should say 4D + 4E = ?

None the wiser with part B

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 Post subject: Re: You lovely people..maths question help please??Posted: Sun Jan 11, 2015 1:48 pm

Joined: Mon Feb 12, 2007 1:21 pm
Posts: 14003
5D + 1E = 5S

3D + 2E = 4S

6E = ?

How could you get the same numbers of Ds in each equation - try this and then get back to me. If I just post the whole solution it won't help you with the next one.

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 Post subject: Re: You lovely people..maths question help please??Posted: Sun Jan 11, 2015 2:10 pm

Joined: Fri Sep 19, 2014 4:32 pm
Posts: 262
I'm getting an answer of 6 squares.. Is that right?

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 Post subject: Re: You lovely people..maths question help please??Posted: Sun Jan 11, 2015 2:32 pm

Joined: Mon Feb 12, 2007 1:21 pm
Posts: 14003
Can you post or PM me your working ? Also double check the original equations as I seem to be getting fractions

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 Post subject: Re: You lovely people..maths question help please??Posted: Sun Jan 11, 2015 3:12 pm

Joined: Sun Sep 22, 2013 6:25 pm
Posts: 144
Location: Cheltenham
AML wrote:
B) [the shapes may not weigh the same as in part (a)]

5D + 1E = 5S

3D + 2E = 4S

6E = ?

The top two scales are in perfect balance. How many squares will be needed to balance the bottom set?

Multiply the 1st equation by 3: 15D + 3E = 15S
Multiply the 2nd equation by 5: 15D + 10E = 20S

Subtract these and the D bit will disappear.

7E=5S

Hmmm. 6E = 5S *6/7

Are you sure you haven't got another typo when you've given us the question?

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 Post subject: Re: You lovely people..maths question help please??Posted: Sun Jan 11, 2015 3:22 pm

Joined: Mon Feb 12, 2007 1:21 pm
Posts: 14003
DebsB - it's better to give a hint rather than a full solution ... yes I hit the same issue, hence my post.

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 Post subject: Re: You lovely people..maths question help please??Posted: Sun Jan 11, 2015 3:38 pm

Joined: Fri Sep 19, 2014 4:32 pm
Posts: 262
arghhh, definitely another typo.

Apologies!

So last line should be 7E ..... (not 6E)

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