Problema Solution
Bret started on a 80-mile bicycle ride at 15 miles per hour. After a time he became a little tired and slowed down to 10 miles per hour for the rest of the trip. The entire trip of 80 miles took 5 1/2 hours. How far had Bret ridden when he reduced his speed to 10 miles per hour?
Answer provided by our tutors
Given:
d=80mi
r1=15mi/h
r2=10mi/h
t=5 1/2h
Let d1= x = the distance he had gone when he reduced his speed
d2=80-x=the distance he traveled after reducing his speed
Equation: t1+t2=t
t=d/r
d1 /r1+d2 /r2=11/2
x/15+(80-x)/10=11/2
30[x/15+(80-x)/10=11/2]30
2x+240-3x=165
2x-3x=165-240
-x=-75
x=75miles
Check:
75/15+(80-75)/10=11/2
5+5/10=11/2
5+1/2=11/2
5 1/2=11/2
11/2=11/2
There you go! :)