Issac drove the first three hours at 44 miles per hour.
Step-by-step explanation:
Given,
Average speed of Isaac = 49 mph
Let,
x be the speed during last three hours.
Speed during first three hours = 4x-172
Average = [tex]\frac{Sum\ of\ terms}{No.\ of\ terms}[/tex]
[tex]49=\frac{(4x-172)+x}{2}\\\\49=\frac{4x-172+x}{2}\\\\49=\frac{5x-172}{2}[/tex]
Multiplying both sides by 2
[tex]49*2=\frac{5x-172}{2}*2\\98=5x-172\\98+172=5x\\270=5x\\5x=270[/tex]
Dividing both sides by 5
[tex]\frac{5x}{5}=\frac{270}{5}\\x=54[/tex]
Speed during last three hours = x = 54 mph
Speed during first three hours = 4x-172 = 4(54)-172 = 216-172 = 44 mph
Issac drove the first three hours at 44 miles per hour.
Keywords: average, division
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