At what rate per cent per annum will a sum of money double in 8 years?

If A's income is 3/5 times of B's income and C's income is 6/5 times of B's income then the ratio of C's income to A's income is -

Two candidates fought an election. One of them got 65% of the total votes casted and won by 420 votes. What is the total number of votes polled if no vote is declared invalid?

The difference between the simple interest and the compound interest on a certain amount at 5% for two years is 25, what is the amount?

Acid and water are mixed in a vessel A in the ratio of 5:2 and in vessel B in the ratio 8:5. In what proportion should quantities be taken out from the two vessels so as to form a new mixture in which the acid and water will be in the ratio of 9:4?

The ratio of spirit and water in two mixtures of 20 litres and 36 litres is 3:7 and 7:5 respectively. Both the mixtures are mixed together. Now the ratio of the spirit and water in the new mixture is 

The acid and water in two vessels A and B are in the ratio 4:3 and 2:3. In what ratio should the liquid in both the vessels be mixed to obtain a new mixture in vessel C containing half acid and half water?

Two containers have acid and water mixed in the ratio 3:1 and 5:3 respectively. To get a new mixture with ratio of acid to water as 2:1, the two types of mixture have to be mixed in the ratio?