Speed of a boat in still water is 6 km/hr and speed of the current is 2 km/hr. If boat takes four hours more in upstream than in the downstream to cover ‘D’ km, then find time take by boat to cover ‘D’ km in still water?

A pipe of diameter ‘d’ can drain a certain water tank in 40 minutes. The time taken by a pipe of diameter ‘2d’ for doing the same job in: 

6 carpenters make 96 windows in 16 days. If 8 carpenters work for 4 days how many windows will they make?

In the given filed the area under triangular shape is

Out of ₹ 20, 000 Narendra gives some amount on loan at simple interest rate 8 % per annum and rest amount at simple interest rate 4 / 3 % per annum. At the end of year he earns ₹ 800. The amount given at 8 % rate will be – 

$$ {\sqrt{784}} × \sqrt{6.25} + 56\%\ of\ 450=?+186$$