Question

What least number must be added to each of the numbers 16, 7, 79 and 43 so that the resulting
numbers are in proportion?

Answer 1

Let the number added be x.
∴ (16 + x) : (7 + x) :: (79 + x) (43 + x)

`(16 +x)/ (7 + x )`= `(79 +x)/(43 + x)`
(16 + x)(43 + x ) = (79 + x )(7 + x )
688 + 16x + 43x + x² = 553 + 79x + 7x + x²
688 - 553 = 86x - 59x

135 = 27x
x = 5

Thus, the required number which must be added is 5.