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July 23, 2014

July 23, 2014

Posted by **MB** on Monday, April 19, 2010 at 3:21pm.

- math -
**MathMate**, Monday, April 19, 2010 at 6:58pmSum of speeds = 208 miles/1.6hr=130 mph

Difference of speeds = 10 mph

Faster train = (sum+difference)/2 mph

Slower train = (sum-difference)/2 mph

Explanation:

let f=faster train, s=slower train

S=sum, D=difference, then

S=f+s

D=f-s

Add:

(S+D)=f+s+f-s=2f

therefore f=(S+D)/2

Simlarly, by subtracting,

S-D = f+s - (f-s) = 2s

therefore s=(S-D)/2

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