John's family visited his grandmother over the weekend. the drive to her house was 2 hours at their usual speed. the trip back took 15 min longer because traffic was bad and they had to drive 5 mph slower. how many miles away is Johns's grandmother's house?

The distance to Johns's grandmother's house is 90 miles.

Speed is the ratio of total distance to total time taken, it is given by:

Speed = distance / time

Let x represent the speed that John used and d represent the distance, hence:

x = d/2

Also when taken 15 minute longer (0.25 hours):

x - 5 = d/(2 + 0.25)

x = d/2.25 + 5

Equating:

d/2 = d/2.25 + 5

d = 90 miles

The distance to Johns's grandmother's house is 90 miles.

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