Which of the following is the largest fraction   $${6\over7},{5\over6},{7\over8},{4\over5} ?$$ 

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 machine is marked at ₹ 6,800 and available at a discount of 10%. The shopkeeper gives another off-season discount to the buyer and sells the machine for ₹ 5,202.  Find the offseason discount. 

A librarian purchased 60 story books for his library. But he found that he could get 4 extra books by spending Rs. 336 more and then the overall average price per book would be reduced by Re 1. The previous average price of each book was 

A train travelling at 48 km/hr crosses an another train half of its length and travelling in opposite direction at 42 km/hr in 12 seconds. It also passes a railway platform in 45 seconds. The length of the railway platform Is

If a²+b²+c² = 2(a – b – c) – 3 then the value of 4a – 3b + 5c is 

What is the value of a when $$ {x^{2(3a+1)}}={x^{3}}$$ ?

A cricketer's average score in 10 innings was 36. In his 11th innings, he scored some runs because of which his average increased to 40. What was his score in 11th innings?