Quantitative Aptitude - Arithmetic Ability Questions

In the following question, select the odd letter/letters from the given alternatives.

If the measure of the interior angle of a regular polygon is 120 deg then how many sides does it have?

Which pair is not similar to the other three?

In a triangle the length of the side opposite the angle which measures 60° is 6√3 cm. What is the length of the side opposite to the angle which measures 90°? 

An equal sum is invested in two different schemes. One scheme gives simple interest and the other gives compound interest (annual compounding). The total interest obtained after 2 years from both the schemes together is Rs 2090. If both the schemes have 18% per annum interest rate, then what is the first year interest (in Rs) of simple interest scheme?

Simple interest on a certain sum of money for 3 years at 5% per annum is Rs. 5250. What will be the compound interest on that sum at the same rate for the same period?

The square root of 3249 is

The number of sides of a regular polygon whose exterior angles are each 72 deg is