Mary invested a certain sum of money in a bank that paid simple interest. The amount grew to $260 at the end of 2 years. She waited for another 3 years and got a final amount of $350. What was the principal amount that she invested at the beginning?  Choices:
A) $220	B) $230	C) $240	D) $200	E) $250
What shall be the rate of interest.? Does that is not required for the calculation?   Not really!   Keep in mind that the interest earned each year will be the same in Simple Interest.   At the end of 2 years, Amount = $260   At the end of 5 years, Amount = $350   This means she earned an interest of $90 in 3 years. Or $30 in each year.   We know that the interest earned each year will be the same.   Therefore she must have earned $60 in 2 years.   Hence Principal Amount = $260 - $60 = $200 Option $200260 -  60= 
<gadget id="calculator">260 -  60</gadget>
<output>200</output>
$200 Option $200
<result>D</result>
Mary invested a certain sum of money in a bank that paid simple interest. The amount grew to $260 at the end of 2 years. She waited for another 3 years and got a final amount of $350. What was the principal amount that she invested at the beginning?