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Question
What least number must be added to each of the numbers 6, 15, 20 and 43 to make them proportional?
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Solution
Let the number added be x.
∴ (6 + x) : (15 + x) :: (20 + x) : (43 + x)
`=> (6 + x)/(15 + x) = (20 + x)/(43 + x)`
`=>` (6 + x)(43 + x) = (15 + x)(20 + x)
`=>` 258 + 6x + 43x + x2 = 300 + 15x + 20x + x2
`=>` 49x – 35x = 300 – 258
`=>` 14x = 42
`=>` x = 3
Thus, the required number which should be added is 3.
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