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Frank and Bob start from home in their cars and travel in opposite directions. Frank's speed is twice of Bob's. In 4 hours they are 480 kilometers apart. Find their speeds.

 Feb 23, 2020
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Let  Bob's  speed  =  B

Then Frank's speed    = 2B

 

So     Rate * Time  =  Total Distance.....so.......

 

B*4   +  (2B)*(4)   =  480    simplify

 

4B +  8B  = 480

 

12B  = 480    divide both sides  by 12

 

B  =  40 km /hr  = Bob's speed

2B  = 80 km/hr  = Frank's speed

 

 

cool cool cool

 Feb 23, 2020

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