By selling an article for Rs. 450, I lose 20%. For what price should I sell it to gain 20% ? 

If A can do a work in 10 days and B can do the same work in 15 days, then how many days will they take to complete the work both while working together?

Two successive discounts of 40% and 20%, respectively, on the marked price of an article are equal to single discount of Rs 988. The marked price (in Rs) of the article is:

If $$ {cot A={n\over{n+1}}}$$ and $$ {cot B={1\over{2n+1}}}$$ then what is the value of cot (A + B)?

A certain sum of money at a certain rate doubles itself in 9 years, then in how many years it will become the same sum will be 5 times of itself?

If then the value of

If 3 ^(X-Y)=27 and 3 ^(X+Y)=243, then X is equal to:

Reflection of the point (-1, 4) in the x-axis is: