A sum of money doubles itself at simple interest in 8 years. What is the rate of interest per annum?
If P doubles, SI = P. R = (SI * 100) / (P * T) = (P * 100) / (P * 8) = 100 / 8 = 12.5%.
A and B can do a piece of work in 12 days and 16 days respectively. If they work together, in how many days will they finish the work?
Combined rate = 1/12 + 1/16 = 7/48 per day. Total time = 48/7 days.
The ratio of two numbers is 3 : 4 and their LCM is 180. Find the smaller number.
Let numbers be 3x and 4x. LCM = 12x = 180 => x = 15. Smaller number = 3 * 15 = 45.
A shopkeeper sells an article for Rs. 450 incurring a loss of 10%. At what price should he sell it to gain 20%?
Cost Price = 450 / 0.9 = Rs. 500. For 20% gain, SP = 500 * 1.20 = Rs. 600.
Find the compound interest on Rs. 10,000 for 2 years at 10% per annum compounded annually.
Amount = 10,000 * (1.$1)^2$ = Rs. 12,100. CI = 12,100 - 10,000 = Rs. 2,100.