SOLUTION: The OfficeJet printer can copy Lisa's dissertation in 8 minutes. The LaserJet printer can copy the same document in 10 minutes. If the two machines work together, how long would th

Algebra ->  Rational-functions -> SOLUTION: The OfficeJet printer can copy Lisa's dissertation in 8 minutes. The LaserJet printer can copy the same document in 10 minutes. If the two machines work together, how long would th      Log On


   



Question 416346: The OfficeJet printer can copy Lisa's dissertation in 8 minutes. The LaserJet printer can copy the same document in 10 minutes. If the two machines work together, how long would they take to copy the dissertation?
Thank you

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Add their rates of copying
In words:
( 1 copy / 8 min ) + (1 copy / 10 min) = (1 copy / x min )
------------
+1%2F8+%2B+1%2F10+=+1%2Fx+
Multiply both sides by the LCD, 40x
5x+%2B+4x+=+40
9x+=+40
x+=+40%2F9
x+=+4.444 min
or about 4 min 27 sec
check answer:
1%2F8+%2B+1%2F10++=+1%2F%2840%2F9%29
.125+%2B+.1+=+9%2F40
.225+=+.225
OK