If Tan⁴x – Tan²x=1 then the value of Sin⁴x + Sin²x is__

A person invested 1100 in a company at compound interest compounded semi-annually. He received 1331 after one year. The rate of interest per annum is 

A rectangular grass plot 80 m × 60 m has two roads, each 10 m wide, running in the middle of it; one parallel to length and the other parallel to breadth. Find the cost of gravelling the roads at ₹ 2 per m². 

The difference between simple interest and compound interest on a certain sum at $$ 12{1\over2}$$ % for 3 years is Rs 125. Find the sum.

ABC is an isosceles triangle with AB = AC, A circle through B touching AC at the middle point of Q, intersects AB at P. Then AP : AB is : 

A number is doubled and 9 is added. If the resultant is tripled, it becomes 75. What is that number? 

A man can row $$7{1\over 2}km/h$$ in still water. If a river running at 1.5 km an hour, it takes him 50 minutes to row to a place and back, how far off is the place? 

A can built a wall in 8 days while B can destroy the same wall in 3 days. A start the work and worked for 6 days, during the last 2 days of which B also joins him. In how many days A can finish the remaining work alone?