Re: Mark has twice as many oranges as George. Tony has 10 fewer
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17 Aug 2020, 16:50
First thing we want to do is find out how many oranges Tony has in terms of George's oranges.
We'll have \(T\) = Tony's oranges, \(G\) = George's oranges, and \(M\) = Mark's oranges.
We have:
\(M = 2G\)
\(T = 2(G+M) - 10\)
Substituting in \(2G\) for \(M\), we have:
\(T = 2(G+2G) - 10\)
\(T = 2(3G) - 10\)
\(T = 6G - 10\) [1]
At this point we can completely ignore Mark, as we're interested in George. This is what trapped me initially.
"When Tony gives 15 oranges to George, George has half the number of oranges that Tony had originally"
This means the following:
\(G + 15 = \frac{T}{2}\)
Or:
\(2G + 30 = T\)
From above, we can substitute in Equation [1] for \(T\) into this equation:
\(2G + 30 = 6G - 10\)
\(40 = 4G\)
\(10 = G\)
And there's our answer, Choice A