The average of ten numbers is 72. The average of the first four numbers is 69 and that of the next three number is 74. The 8^th number is 6 more than the 9^th number and 12 more than the 10^th number. What is the average of the 8^th and 9^th numbers?

Two cones have their heights in the ratio 1:3 and the radii of their bases in the ratio 3:1. Find the ratio of their volumes?

$$\sqrt{x}÷ \sqrt{144} = 0.02, $$ then the value of x is 

One angle of a triangle is 55°. If the other two angles are in the ratio 9:16, find the angles?

A rational number between $${3\over4} $$ and $${3\over8} $$ is :

If $${(2cos^3 A-cosA)\over (sin A- 2 sin^3 A)=1}$$ then what is the value of A?

The compound interest on 12000 for 9 months at 20 % per annum , interest being compounded quarterly is 

Find the area of the circle formed in an equilateral triangle of side 42 cm. Using (π=22/7)