nkmungila wrote:

Abigail used to save 40% of her salary in 2013. Her salary increased by 100% in 2014 and by 50% in 2015, but her expenses remained the same throughout. What was the percentage increase in her annual savings over the two years?

A. 200%

B. 240%

C. 300%

D. 500%

E. 600%

We can let Abigail's salary in 2013 = n, and thus her savings = 0.4n and her expenses = 0.6n in that year.

In 2014, her salary has increased by 100%, which means that it has doubled. Her salary, therefore, is 2n.

In 2015, her salary has increased by 50%, so we increase 2n by 50%, which is the same as multiplying it by 1.5:

2n x1.5 = 3n

Since her expenses are the same throughout the years, her expenses are 0.6n in 2015. Thus, she saves 3n - 0.6n = 2.4n in 2015.

We use the percent increase formula: (New - Old)/Old x 100. Thus, the percentage increase from 2013 to 2015 is (2.4n - 0.4n)/0.4n x 100 = 2.0n/0.4n x 100= 20/4 x 100 = 5 x 100 = 500%.

Answer: D

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