Ram lent Rs. 6,000/- to Shiva for 3 years and Rs. 8,000/- to Krishna for 5 years at the same rate of simple interest per annum. He got a total interest of Rs. 5,220 from both. Find the rate of interest per annum.
A truck moves at the speed of 90 km/hr after repairing and moves at the speed of 80 km/hr before repairing. It covers x distance in 8 hours after repairing. How much time (in hours) will it take to cover 4x distance before repairing?