DSGB wrote:
A boat traveled upstream 90 miles at an average speed of (v-3) miles per hour and then traveled the same distance downstream at an average speed of (v+3) miles per hour. If the trip upstream took a half hour longer than the trip downstream, then how many hours did it take the boat to travel downstream?
A. 2.5
B. 2.4
C. 2.3
D. 2.2
E. 2.1
let t=downstream hours
v+3=90/t
v-3=90/(t+1/2)
subtracting,6=90/t-[90/(t+1/2)] ➡
2t^2+t-15=0
(2t-5)(t+3)=0
t=2.5 hours
A
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