Pipe A can fill an empty cistern in 4 hours while along with Pipe B it can fill it up in 3 hours. Only Pipe A is turned on for an hour after which Pipe B is also turned on. How much total time will it take to fill up the cistern?
M borrowed some money for 1 year at certain simple interest. But the interest rate was increased to 2% which amounted to Rs.120. Find the principal amount.