Which of the following fraction is the smallest?

$$7\over 6 $$,$$7\over 9$$,$$4\over 5$$,$$5\over 7$$

A person invests a certain amount on simple interest. After 8 years he gets 16% interest. If he invests the same sum for 4 years, then he gets Rs. 9600 as interest, then the sum is

Average weight of 25 students of a class is 50 kg. If the weight of the class teacher is included, the average is increased by 1 kg. The weight of the teacher is 

In 80 litres mixture of milk and water the ratio of amount of milk to that of amount of water is 7: 3. In order to make this ratio 2: 1, how many litres of water should be added?

Compute the compound interest on ₹ 8,400 for one and half years at 12% rate of interest per annum, compounded half yearly.

Sujata marks the marked price of an article at 36% above the cost price and allows 40% discount on the marked price then what is the loss percentage?

The ratio of two whole numbers is 5 : 7. Which of the following can be their sum?

On a river, Q is the mid-point between two points P and R on the same bank of the river. A boat can go from P to Q and back in 12 hours, and from P to R in 16 hours 40 min. How long would it take to go from R to P?