Working together, John and Jack can type 10 pages in one hour. If they would be able to type 12 pages in one hour if Jack increases his typing speed by 25%, what is the ratio of Jack's normal typing speed to that of John? Choose the correct choice
A) 3/1 B) 1/3 C) 4/1 D) 1/4 E) 5/4
Lets say John types x pages an hour and Jack types y pages an hour.   We know that x+y=10   Jack increase speed by 25% means he will type 1.25y pages an hour.   So we get x+1.25y=12   We need to know the ratio of Jack's speed to John's speed. This is going to be proportional to the number of pages each can type in an hour, hence (y/x).   Subtracting both : 0.25y=2 so y=8 ... so x=2   (y/x)=8/2= 
<gadget id="calculator">8/2</gadget>
<output>4</output>
4/1   Answer is (4/1)
<result>C</result>
Working together, John and Jack can type 10 pages in one hour. If they would be able to type 12 pages in one hour if Jack increases his typing speed by 25%, what is the ratio of Jack's normal typing speed to that of John?