X and Y together can do a work in 2(2/5) days. Y and Z together can do the same work in 3 days. X and Z together can do the same work in 4 days. The time taken by X, Y and Z together to do the same work is:
The average of the squares of four consecutive even natural numbers is 126. The average of 8 times of the greatest number and 5 times of the smallest number is: