Question

What least number must be added to each of the numbers 6, 15, 20 and 43 to make them proportional?

Answer 1

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.