SOLUTION: A man drove 156 km at a constant rate. If he had driven 5km/hr. faster he would made the trip in 12 minutes less time. How fast did he drive?
ans. 60 KPH
help me with solutio
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Question 683843: A man drove 156 km at a constant rate. If he had driven 5km/hr. faster he would made the trip in 12 minutes less time. How fast did he drive?
ans. 60 KPH
help me with solution pls..
Found 2 solutions by josmiceli, lwsshak3:
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Let = his speed in km/hr
= his speed plus km/hr
Let = his time to travel 156 km
his time minus min
as fraction of an hour
------------------
Equation for actual trip:
(1)
Equation for 5 km/hr faster:
(2)
-----------------------------
(2)
and
(1)
Substitute (1) into (2)
(2)
(2)
(2)
(2)
Multiply both sides by
(2)
(2)
Use quadratic equation:
( ignore the negative square root )
His speed was 60 km/hr
check:
(1)
(1)
(1)
and
(2)
(2)
(2)
(2)
OK
Answer by lwsshak3(11628) (Show Source): You can put this solution on YOUR website!
A man drove 156 km at a constant rate. If he had driven 5km/hr. faster he would made the trip in 12 minutes less time. How fast did he drive?
ans. 60 KPH
**
let x=how fast he drove
x+5=speed in 12 min less time
156/x-156/(x+5)=12 min=12/60 hr=0.2 hr
156/x-156/(x+5)=.2
LCD: x(x+5)
156(x+5)+156x=x(x+5)(.2)
156x+780+156x=.2x^2+x
.2x^2+x-780=0
2x+10x-7800=0
x+5x-3900=0
(x+65)(x-60)=0
x+65=0
x=-65(reject, x>0)
or
x-60=0
x=60
how fast he drove=60 km/hr
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