A couple who own an appliance store discover that if they advertise a sales discount of 10% on every item in the store, at the end of one month the number of total items sold increases 15%. Their gross income from sales for one month increases by what percent?  Answers:
A) 1.5%
B) 2.5%
C) 3.5%
D) 4.5%
E) 5.5%
Let P be the original price and let x be the number of items sold originally.   The original income is P*x.   After the changes, the income is 0.9P*1.15x = 1.035*(P*x), an increase of 3.5%.   The answer is 3.5%.0.9 *1.15= 
<gadget id="calculator">0.9 *1.15</gadget>
<output>1.035</output>
1.035*(P*x), an increase of 3.5%.   The answer is 3.5%.
<result>C</result>
A couple who own an appliance store discover that if they advertise a sales discount of 10% on every item in the store, at the end of one month the number of total items sold increases 15%. Their gross income from sales for one month increases by what percent?