It takes Jack 2 more hours than Tom to type 20 pages. If working together, Jack and Tom can type 25 pages in 3 hours, how long will it take Jack to type 40 pages?	Choose one:  A) 5  B) 6  C) 8  D) 10  E) 12
let's take answer choice D -10 h   if it took 10 h for 40 pages, then it took 5 hours for 20 pages   since it takes Jack 2 more hours than Tom to type 20 pages, Tom's time is 5-2= 
<gadget id="calculator">5-2</gadget>
<output>3</output>
3 h   their combo time 5*3 /(5+3)=15/8   if it takes 3 h for 25 pages, then it will take 12/5 h ( =20*3/25) for 20 pages   as u see 15/8 &lt;12/5 . so D is out, and we should check 12, whose number is more than D's   answer choice 12 = 12 for 40 pages or 6 for 20 pages   then Tom's time =6-2= 
<gadget id="calculator">6-2</gadget>
<output>4</output>
4 h   combo time=6*4/(6+4)=12/5   if it takes 3 h for 25 pages, then it will take 12/5 h ( =20*3/25) for 20 pages   12/5=12/5   answer choice 12
<result>E</result>
It takes Jack 2 more hours than Tom to type 20 pages. If working together, Jack and Tom can type 25 pages in 3 hours, how long will it take Jack to type 40 pages?