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1. Hi

What do I do when met with a typical question such as

Mr Harris had a party, he bought some bottles of lemonade costing 75p each and some bottles of orange juice costing 82p each. Altogether he spent £71.94. How many bottles of orange juice did he buy?

I know the trial and error method, but I hate, hate, hate that method with a passion, so I was wondering if I can do it another way, say, using algebra?

thanks!
2. Substitution
Let qty orange = g
Let qty lemon.. = n

We know g+n= 75+82 = 157
and
75n + 82g = 7194

So if g+n = 157 then n = 157-g

Substitute n into bigger eq,

75(157-g) + 82g = 7194

Then solve for g with algebraic manipulation.
Then substitute g again into 75n + 82g = 7194 to get n.

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Updated: April 9, 2013
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