Find the average of the cubes of the first five natural numbers. 

A man can row 10 km/h in still water. When the river is running at a speed of 4.5 km/h, then it takes him 2 h to row to a place and comes back to the initial point . How far is the place (in km) (rounded off to two decimal places)?

In ΔPQR, PQ=QR and O is an interior point of ΔPQR such that ∠OPR=∠ORP.

Consider the following statements:

(i) ΔPOR is an isosceles triangle.

(ii) O is the centroid of ΔPQR.

(iii) ΔPQO is congruent to ΔRQO.

Which of the above statements are correct?

Evaluate the following.

sin 25° sin 65° – cos 25° cos 65°.

A man buys a machine for Rs.5,000. After one year, he sells it for Rs.6000. After two years, again he buys the same machine at Rs.8,000 and sells it for Rs.10,000. Find his overall profit percentage for both the transactions.

The product of the two numbers is 1500 and their HCF is 10. The number of such possible pairs is/are: 

Find the value of the given expression.

 $$\sqrt { 8+\sqrt { 1681} \ } \ $$

If radius of a sphere is decreased by 48%, then by what percent does its surface area decrease?