For the following questions answer them individually
Pipes P and Q can fill a tank in 20 and 16 hours respectively. Pipe Q alone was opened for $$\frac{1}{4}$$ of time and later P also was opened. In how many hours was the tank filled?
The sum of the digits of a two-digit number is 9 less than the number. Which of the following digits is at ten's place of the number ?
In which type of waves do the vibrations move parallel to the direction of travelling of wave ?
P and Q run around a circular track of 240 m at 15 m/min and 20 m/min speeds respectively. If they start running simultaneously, after what time will they meet again at the starting point?
Find the least number that should be added to 2497 so that the sum is divisible by 5, 6, 4 and 3.
