If $a, b, c$ are in geometric progression and $a + b + c = 21$, $abc = 216$, what is the value of $b$?
The cost price of an article is Rs. 200. It is sold at a 10% discount on the marked price, yielding a 25% profit. What is the marked price?
If $x^2 + y^2 = 25$ and $xy = 12$, what is the value of $x + y$?
A shop sells two types of pens at Rs. 10 and Rs. 15 each. If 50 pens are sold for Rs. 650, how many pens of Rs. 10 were sold?
A shopkeeper marks up an article by 25% and then offers a 20% discount. What is the net profit percentage?