A store owner buys cell phones for 40.00 and marks up the price by 25%. explain how to find the price at which she sells the cell phones.

We use proportion in this problem solving.

We know that 100% = 40.00 and 125%=x

I take 125% because the marks the price up 25%. So it is 100%+25%.

100x=40.00*125

x=40.00*125:100

x=50.00

So the she sells the cell phone at 50.00