Jamal can type a 20 page document in 40 minutes, Saeed can type it in 30 minutes, and Zahid can type it in 24 minutes. Working together, the time will in take them to type the same document is _____

Jameel types 20 Pages=40 minutes
Jameel type 1 Page=20/40=1/2
Saeed type 20 Page=30 minutes
Saeed type 1 Page=20/30=2/3
Zahid type 20 Pages=24 minutes
Zahid type 1 Page=20/24=5/6
1 Page typing average=1/2+2/3+5/6=(3+4+5) / 6 = 12/6=2
20 pages typing average=20/02=10 minutes