The pool is filled through a narrow pipe in 10 hours, and through a wide one in 4 hours.

The pool is filled through a narrow pipe in 10 hours, and through a wide one in 4 hours. Which pipe gives less water: wide in 3 hours or narrow in 7 hours?

Through a narrow pipe, the pool is filled in 10 hours, in one hour it will fill 1/10 of the pool. In 7 hours, the pipe will fill 7 * 1/10 = 7/10 part of the pool.

Through a wide pipe, the pool will be filled in 4 hours, which means that 1/4 of the pool will be filled in 1 hour. In 3 hours, the pipe will fill 3 * 1/4 = 3/4 part of the pool.

Let’s compare two fractions: 7/10 and 3/4. For comparison, let us bring them to a common denominator.

It will turn out to be 14/20 and 15/20. Since 14/20 <15/20, a narrow pipe produces less water in 7 hours than a wide one in 3 hours.