Andrea invested a certain sum of money in a bank that paid simple interest. The amount grew to $340 at the end of 2 years. She waited for another 4 years and got a final amount of $420. What was the principal amount that she invested at the beginning? Choose the correct choice from the following options:
A) $350	B) $300	C) $400	D) $375	E) $360
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 = $340   At the end of 6 years, Amount = $420   This means she earned an interest of $80 in 4 years. Or $20 in each year.   We know that the interest earned each year will be the same.   Therefore she must have earned $40 in 2 years.   Hence Principal Amount = $340 - $40 = $300 Option $300340 -  40= 
<gadget id="calculator">340 -  40</gadget>
<output>300</output>
$300 Option $300
<result>B</result>
Andrea invested a certain sum of money in a bank that paid simple interest. The amount grew to $340 at the end of 2 years. She waited for another 4 years and got a final amount of $420. What was the principal amount that she invested at the beginning?