A certain sum of money lent out at simple interest amounts to Rs. 2400 in 4 years and Rs. 3000 in 6 years. Find the rate of interest per annum?

Sanjay invested Rs. 48000 in two different parts one at 10% CI (Compounded half yearly) and another one at 15% SI. At the end of the year he received total interest Rs. 5490, then find the amount invested in SI?

α and β  is two root of a equations $$2x^2-7x+ 12=0 $$ then the value of $$ {α \over β }  + {β \over α }=? $$

An alloy contains copper and tin in the ratio 3: 2. If 250 gm of copper is added to this alloy then copper in it becomes double the quantity of tin in it. What is the amount (in gm) of tin in the alloy? 

Find the sum of all prime numbers between 10 and 90.

A boat running downstreams covers a distance of 30 kms in 2 hours. While coming back the boat takes 6 hours to cover the same distance. If the speed  of the current is half that of the boat, what is the speed of that boat in kmph?

The expenses on rice, fish and oil of a family are in the ratio 12 : 17 : 3. The price of these articles are increased by 20 % , 30 % and 50 % respectively. The total expenses of family on these articles are increased by: