18 pipes of equal capacity fills the tank in 20 minutes. How many pipes of equal capacity may be required to fill the tank exactly in 15 minutes ? समान क्षमता वाले 18 नल पानी की टंकी को 20 मिनट में भर देते हैं | उसी नल को 15 मिनट में भरने के लिए समान क्षमता वाले कितने नलों की आवश्यकता होगी ?

18 pipes fill tank in 20 minutes. This is an inverse proportion: more pipes = less time. 18 × 20 = X × 15, where X is required pipes. X = (18 × 20)/15 = 360/15 = 24 pipes. The work (filling the tank) is constant. Pipes × Time = Constant. When time decreases from 20 to 15 minutes (factor of 3/4), pipes must increase by factor 4/3: 18 × 4/3 = 24.