Ann invested a certain sum of money in a bank that paid simple interes

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 = $240
At the end of 5 years, Amount = $300

This means she earned an interest of $60 in 3 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 = $240 - $40 = $200 Option C

Does this help?

Ann invested a certain sum of money in a bank that paid simple interest. The amount grew to $240 at the end of 2 years. She waited for another 3 years and got a final amount of $300. What was the principal amount that she invested at the beginning?

A. $150
B. $175
C. $200
D. $210
E. $220

Amount after 5 years = $300
Amount after 2 years = $240
Difference in Amount for 3 years = 300-240 = $60
Interest earned for 3 years is $60.
Therefore interest earned for 1 year = 60/3 = $20
Thus interest earned for 2 years = 2 x 20 = $40
Amount after 2 years = $240
Therefore Principal amount = Amount after 2 years - Interest = 240 - 40 = $200
Answer C...

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