6 pumps of kirlosker can fill a tank in 7 days and 2 similar pumps of USHA can fill the same tank in 18 days. what is the ratio of the efficiency of a kirlosker pump and a USHA pump?

The number of days required by a single kirlosker pump to fill the tank = 6 x 7 =42 days and the number of days required by a single USHA pump to fill the same tank = 2 x 18 =36 days.

Now , since efficiency is inversely proportional to the number of days. Hence,

$\frac{Efficiency of one K - pump}{Efficiency of U- pump}=\frac{36}{42}=\frac{6}{7}$