Question
Find the fourth proportion of (5k + 5), (10k + 10) and
(15k + 15). (Note: 'k' is the smallest prime number.)Solution
'k' = 2 5k + 5 = 5 Γ 2 + 5 = 15 10k + 10 = 10 Γ 2 + 10 = 30 15k + 15 = 15 Γ 2 + 15 = 45 Let the fourth proportion be 'm'. 15 : 30 :: 45 : m So, 15 Γ m = 30 Γ 45 Or, 'm' = 90
