Hi sukhman,
This question can be solved by TESTing THE ANSWERS.
We're told that an invest = $1500 and that by raising the interest rate on that $1500 by 2 percentage points the interest would equal $90. We're asked for the ORIGINAL interest rate.
$1500 is a nice "round" number; 1% of $1500 = $15, so calculating any other percent of $1500 will be pretty straight-forward. Three of the answers are also nice round numbers, so let's start with....
Answer B: 4%
If the original interest was 4%, then the new interest = 4+2 = 6%
6% of $1500 = $90
This is an exact MATCH for what we were told, so this must be the answer.
Final Answer: B
GMAT assassins aren't born, they're made,
Rich