Question 257106
Your speed=30 mph
Mom'sspeed=78 mph
Approach velocity=78-30=48 mph
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At 7:51 distance between mom & you=30*(7:51-7:46)/60
=30*5/60=2.5 miles

mom appraches 48 miles in one hr = 60 minutes
so to cover 1 mile mom will take 60/48=1.25 minutes
to cover 2.5 miles mom will take = 1.25*2.5=3.125 minutes
so mom will meet you at 7:51+3.125=7:54 and 1/8 of a minute