The circumferences of two circles are 132 metres and 176 metres respectively. What is the difference between the area of the larger circle and that of the smaller circle?

Arun invested a sum of money at a certain rate of simple interest for a period of four years. Had he invested the same sum for a period of six years, the total interest earned by him would have been fifty percent more than the earlier interest amount. What was the rate of interest percent per annum?

180-metre long train crosses another 270- metre long train running in the opposite direction in 10.8 seconds. If the speed of the first train in 60 kmph, what is the speed of the second train in kmph?

The ratio of the age of a father and a son at present is 5: 2. Four years hence the ratio of the ages of the son and his mother will be 1 : 2. What is the ratio of the present ages of the father and the mother?

If the numerator of a fraction is increased by 150% and the denominator of the fraction is increased by 350%, the resultant fraction is $25\over51$ . What is the original fraction?