A retailer buys 30 pens from a wholesaler and pays equal to marked price of 27 pens. If he sells the pens at the marked price, his profit per cent in the transaction is

Ten years ago A was half of B in age. If the ratio of their present ages is 3 : 4, what will be the total of their present ages?

If the diameter of a cylinder is 20 cm and its height is 20 cm, then the surface area (in cm²) is

The ratio between the length and breadth of a rectangular field is 3 : 2. If the length is increased by 5 m, the new area of the field will be 2600 sq m. What is the breadth of the rectangular field?

45% of √225 + 21 = ?

If a sum of money doubles itself in 8 yr at simple interest, then the rate of interest per annum (in %) is

40 ÷ 0.80 ÷ 0.25 = ?

6085 − 4017 + 1496 − 1124 = ?

A contractor agreeing to finish a work in 150 days employed 75 men, each working for 8 h daily. After 90 days only 2/7 of the work was completed. How many more men would be put on now, each working 10 h daily so as to finish the work in the stipulated time?