# Calculating the next proportional.

How did they come up with 24 to the following ?

Calculate the 4th proportional to 5,8,15 ?

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4 can't be the solution. –  Aang Jul 3 '12 at 6:32
Sorry that was a misprint - I meant 24 –  MistyD Jul 3 '12 at 6:33
$\frac{5}{8}=\frac{15}{x}$ which gives you $24$ –  Saurabh Jul 3 '12 at 6:33
Agree with @SaurabhHota. –  Aang Jul 3 '12 at 6:37
@SaurabhHota Thanks ..That was simple –  MistyD Jul 3 '12 at 6:40

$5:8 :: 15:x$ implies $5x = 15\times8$.