# Andy’s average driving speed for a 4-hour trip was 45 miles per hour. During the first 3 hours he drove 40 miles per hour. What was his average speed for the last hour of his trip?

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by Allanaiz719

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by Allanaiz719

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where v average in this problem is 45mph

v1 = 40mph

v2 = 40mph

v3 = 40mph

t = 4hours

you are asked to find v4

by substituting the given values you'll have:

cross multiply 4 and add the values at the right side

180 = 120 + v4

v4 = 180 - 120