It takes Jim N minutes to prepare one omelet. It takes Cole N/2 minutes to prepare one omelet. It takes Mitch N/2 minutes to prepare 2 omelets. If Jim, Cole and Mitch together prepare a total of 30 omelets in 40 minutes, then how many minutes would it take Mitch alone to prepare 30 omelets?
Select:
A) 70
B) 120
C) 140
D) 160
E) 280
Cole is twice as fast as Jim and Mitch is 4 times as fast as Jim (it takes Mitch N/2 minutes to prepare 2 omelets, thus N/4 minutes to prepare one omelet).   Say the rate of Jim is x omelet/minute, the rate of Cole 2x omelet/minute, and the rate of Mitch 4x omelet/minute.   Then, from (time)(rate) = (job done):   (40 minutes)(x + 2x + 4x) = (30 omelets);   (40 minutes)(7x) = (30 omelets);   Since it takes 40 minutes to prepare 30 omelets at the rate of 7x omelet/minute, then it would take   40*7/4= 
<gadget id="calculator">  40*7/4</gadget>
<output>70</output>
70 minutes to prepare the same 30 omelets at the rate of 7x*4/7 = 4x omelet/minute (the rate of Mitch).   Or:   (40 minutes)(7x) 7 *4/7= 
<gadget id="calculator">7 *4/7</gadget>
<output>4</output>
4x omelet/minute (the rate of Mitch).   Or:   (40 minutes)(7x)= (30 omelets);   (40*7/4 minutes)(7x*4/7) = (30 omelets);   (70 minutes)(4x) = (30 omelets);   70nswer: 70.
<result>A</result>
It takes Jim N minutes to prepare one omelet. It takes Cole N/2 minutes to prepare one omelet. It takes Mitch N/2 minutes to prepare 2 omelets. If Jim, Cole and Mitch together prepare a total of 30 omelets in 40 minutes, then how many minutes would it take Mitch alone to prepare 30 omelets?