If the angle of elevation of the Sun changes from 30° to 45°, the length of the shadow of a pillar decreases by 20 meters . The height of the pillar is:
If 4 men and 6 boys can do a work in 8 days and 6 men and 4 boys can do the same work in 7 days, then how many days will 5 men and 4 boys take to do the same work?
For doing a certain work, the efficiencies of A, B and C are in the ratio 2 : 3 : 5. Working together, they can complete the same work in 15 days. B and C can complete 80% of the original work in: