If a : b = 7 : 9 and b : c = 5 : 7, then what is a : c ?

A train is traveling at the rate of 45km/ hr. How many seconds will take to cover a distance of $$ {4\over5} $$ km? 

A train runs at a speed of 80km/hr. If the length of the train is 400 m, how long will it take for it to cross an 400m bridge? 

A man invested a sum of money in Scheme A, at a rate of 15% per annum for simple interest, at the end of 2 years the amount received by him is invested in scheme B at 20% per annum for compound interest. If the interest received by him from scheme B at the end of 2 years is Rs. 2860, then find the sum invested by man in the beginning?

A sum of Rs. 2000 at 40% per annum compounded annually. Calculate the interest for the third year at compound interest.

A person borrows some money for 5 years and the ratio of the loan amount: total interest amount is 5 : 2. Then find the ratio of the loan amount: interest rate is equal to 

The numbers 1, 3, 5, 7______99 and 128 are multiplied together. The number of zeros at the end of the product must be: