In a family, the consumption of power is 120 units or 18 days. Find how many units of power is consumed in 30 days.

Explanation

Let the consumption of power in 30 days be x units
The more the period of time, the more is the consumption of power. Hence the consumption of power varies directly as the number of days.
` :. ` (Ratio of number of days ) :: (Ratio of consumption of power)
` rArr 18 : 30 :: 120 : x`
Product of means = Product of extremes
` rArr 30 xx 120 = 18 xx x rArr x = (30 xx 120)/18 = 200 ` units.
`:. ` The consumption of power for 30 days is 200 units.