The sum of 10 terms of the arithmetic series is 390. If the third term of the series is 19. Find the first term

A scientist mixes 10% water in his solution but he is not content with it so he again mixes 10% more water in the previous mixture. What is the profit percentage of the scientist if he sells it at cost price:

Krishna bought a camera and paid 20 % less than its original price. He sold it at 40 % profit on the price he had paid. The percentage of profit earned by Krishna on the original price was 

A man standing on the bank of river observes that the angle subtended by a tree on the opposite bank is 60°. When he retrieves 36 m from the bank, he find that the angle is 30°. The breadth of the river is

If each edge of a cube is reduced by 25 percent, find the ratio of the volume of the original cube and the resulting cube?

If the instalments are paid at the end of every year, what annual payment will discharge a debt of Rs. 7,200 due in 3 years at 20% per annum simple interest?

A field is in the form of an equilateral triangle of side 100 m. A horse is tied to a vertex of the field, with a 15 m long rope. Over what area can the horse graze?