A trader marked his goods at 20 % above the cost price. He sold half the stock at the marked price. one quarter at a discount of 20 % on the marked price and the rest at a discount of 40 % on the marked price. His total gain is 

If  $${3-5x\over 2x}+{3-5y\over 2y}+{3-5z\over 2z}=0$$ then the value of  $${2\over x}+{2\over y}+{2\over z}$$ is:

If  $$ \ {xy\over x+y}= a, $$ $${xz\over x+z}=b $$ and $$ {yz\over y+z} =c $$  where a, b, c are all non – zero numbers, then x equals to

Ratio of age of father, mother and son is 9:8:3. Five years hence sum of their age will be 95 years. Find the age of son 5 years ago.

A train is traveling at the rate of 45km/ hr. How many seconds will take to cover a distance of $$ {4\over5} $$ km? 

The reduction of Rs . 12 in the selling price of an article will changes 5 % gain into  $$ 2{1\over 2}\% $$ loss . The cost price of the article is 

A racing car going at an average speed of 108 km/ hr takes 15 minutes to complete a lap on a racing track. By how much should it increase its speed (in km/hr) to complete the lap in 12 minutes?