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 Post subject: Help me again please
PostPosted: Mon Apr 19, 2010 2:17 pm 
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Joined: Tue Sep 01, 2009 3:38 pm
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Location: Maidstone
1. In a safari park there are elephants and penguins. Altogether there are 24 heads and 64 feet. How many elephants are there?

2. Find two numbers a sum of 28 where one number in three times the other.

3. Find two numbers a sum of 84 where one number is 16 more than the answer.

I dont have the answers as they are sample questions. Can you please show me how you worked the answers. Thanks

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 Post subject:
PostPosted: Mon Apr 19, 2010 2:26 pm 
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Joined: Wed May 09, 2007 2:09 pm
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Location: Solihull, West Midlands
1. Put E= no of elephants, P= no. of penguins

Then E+P= 24
4E + 2P= 64

Double first equation:
2E + 2P= 48

Subtract this from 2nd equation

2E = 64-48 = 16 so E=8

There are 8 elephants and 16 penguins

2. x + 3x = 28 so x=7

3. x+y = 84, y=x+16 so 2x+16 = 84, 2x= 84-16 = 68, x=34

Numbers are 34 and 50


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 Post subject: Re: Help me again please
PostPosted: Mon Apr 19, 2010 2:27 pm 
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Posts: 1326
Location: Watford, Herts
They can all be done with algebra, but I'll try without.
sherry_d wrote:
1. In a safari park there are elephants and penguins. Altogether there are 24 heads and 64 feet. How many elephants are there?

Elephants and penguins have one head apiece, so there are 24 animals. If they were all penguins, there would be 48 feet. The extra 16 feet must belong to 8 elephants, and the other 16 animals are penguins.
sherry_d wrote:
2. Find two numbers a sum of 28 where one number in three times the other.

This means the sum is 4 times the other number, which must be 28/4 = 7, and the first number is 21.
sherry_d wrote:
3. Find two numbers a sum of 84 where one number is 16 more than the answer.

This means 84-16 = 68 must be twice the smaller number, which must be 34, and the larger one is 50.


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 Post subject:
PostPosted: Mon Apr 19, 2010 2:28 pm 
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Location: Solihull, West Midlands
I'm glad we agree!


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 Post subject:
PostPosted: Mon Apr 19, 2010 2:37 pm 
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Location: Watford, Herts
solimum wrote:
I'm glad we agree!

Me too!

Of course children should always be encouraged to check their answers by plugging them into the original question.


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 Post subject:
PostPosted: Mon Apr 19, 2010 2:46 pm 
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Joined: Wed Sep 23, 2009 12:47 pm
Posts: 698
Location: Essex
First one:

64 =4e+2p (64 is total of feet, e's have 4 feet and p's have 2)
24 =e+p (24 is total of heads and e plus p must equal that number)

so, changing sides and signs etc, gives you

2p=64-4e and p=24-e

so

2(24-e) =64-4e

48 -2e=64-4e

48+2e=64

2e=64-48

2e=16

e=8

8 elephants. If you'd been asked about the penguins, you'd have substituted for e instead of p.


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 Post subject:
PostPosted: Mon Apr 19, 2010 3:01 pm 
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Location: Maidstone
Thank you all, I struggle a bit with algebra. Are there some resource you can point me towards? DD hasnt done them yet so I have to teach her the basics so anything that can help her or me. The 11+ books I have hardly touch the equations. WP you put me to shame, you make it seem so easy and yet I have my eyes out right now trying to make head and tail of it all :oops:

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 Post subject:
PostPosted: Mon Apr 19, 2010 6:19 pm 
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Joined: Sat May 17, 2008 8:37 am
Posts: 111
Have a look here for algebra explanations. I found this site good for many maths things.

http://www.mathsisfun.com/algebra/index.html


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 Post subject:
PostPosted: Mon Apr 19, 2010 7:44 pm 
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Joined: Fri Oct 12, 2007 12:42 pm
Posts: 3813
Location: Chelmsford and pleased
Some worksheets here
http://www.math-drills.com/algebra.shtml
(Solving linear equations section)

I always get reluctant children to shop

E.g.

I started the day with £25 but now I only have £5 and 5 books. How much did each book cost?

5b + 5 = 25

Children can see that they spent £20 so the books must have cost £4 each.

If you look at the worksheets then you can call the letters whatever you want, Doctor Who characters has worked well in the past, but whatever takes your child's fancy.

3C + 5 = £20

I now have three cybermen and £5. How much were the cybermen?


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 Post subject:
PostPosted: Mon Apr 19, 2010 8:47 pm 
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Joined: Tue Sep 01, 2009 3:38 pm
Posts: 2083
Location: Maidstone
Thanks Moved and Rosepetal for the links.

When given the basic equation its not too hard but becomes a little trick when its given as above and I notice in the link you gave me they have some question similar in the Translating Algebraic Phrases. Thats should really help.

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