SOLUTION: Question: Steve and Michael are in their boat headed upstream. They travel a distance of 15 miles to the nearest beach. The speed of the current is 4 miles per hour. The total trip
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Question 589633: Question: Steve and Michael are in their boat headed upstream. They travel a distance of 15 miles to the nearest beach. The speed of the current is 4 miles per hour. The total trip to the beach takes 7 hours. What is the speed of the boat?
My work: I thought I could try using a variation of t=d/r
I thought I could do (30/(x-4))+(30/(x+4))=7 where x=speed of the boat
Is this the correct way to solve the problem?
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
Boat speed x mph
current speed 4 mph
against current x- 4 mph
with current x+ 4 mph
Distance=15 miles
Time against + time with =7hours
t=d/r
15/(x+4) +15/(x-4)=7
LCD =(x-4)(x+4)
15*(x-4) +15(x+4) = 7
15x-60+15x+60=7(x ^2-16)
30x=7x ^2-112
7x ^2-30 x-112
Find the roots of the equation by quadratic formula
a= 7 , b= -30 , c= -112
b^2-4ac= 900 + 3136
b^2-4ac= 4036
x1=( 30 + 63.53 )/ 14
x1= 6.68
x2=( 30 -63.53 ) / 14
x2= -2.39
Ignore negative value
Boat speed 6.68 mph
m.ananth@hotmail.ca
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