In what time will ₹ 72 become ₹ 81 at $$6{1\over4}$$ % per annum simple interest?

Mohan lent some amount of money at 9% simple interest and an equal amount of money at 10% simple interest each for two years. If his total interest was Rs. 760, what amount was lent in each case?

A lends 2500 to B and a certain sum to C at the same time at 7% annual simple interest. If after 4 years, A altogether receives 1120 as interest from B and C, the sum lent to C is-

If the average marks of three batches of 55, 60 and 45 students respectively is 50, 55 and 60, then the average marks of all the students is?

12 kg of rice costing 30 per kg is mixed with 8 kg of rice costing 40 per kg. The average per kg price of mixed rice is

The average weight of five persons sitting in a boat is 38 kg. The average weight of the boat and the persons sitting in the boat is 52kg. What is the weight of the boat?

The average of the marks obtained in an examination by 8 students was 51 and by 9 other students was 68. The average marks of all 17 students was: 

The average monthly expenditure of a family for the first four months is ₹ 2570, for the next three months ₹ 2490 and for the last five months ₹3030. If the family saves ₹ 5320 during the whole year, the average monthly income of the family during the year is-