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syanjaali
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Posted on 03-31-11 12:10
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Answer is 8 and 6 hrs drove 360 miles. How to create a equation?
Question: A truck is driving 45mph and a car is traveling at 60 mph. The car and the truck are traveling the same distance. The truck travels 2 hours longer than the car. How many hours did each travel?
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perfectionist
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Posted on 03-31-11 12:19
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Let, x b hrs truck drove. so in x hrs, truck covered: 45*x miles
since car drove 2 hrs less than x, car covered: 60* (x-2) miles
as u mentioned, both covered equal distance:
45*x=60* (x-2)
ie, x = 8 hrs
x-2 = 6 hrs
miles covered = 6*60 or 8*45 = 360 miles
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Stiffler
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Posted on 03-31-11 12:20
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Velocity=Distance travelled/ time taken
V=D/T
Thus, T=D/V
Given, V(truck)=45 mph
V(car)=60 mph.
Assume they both travel D miles of distance.
Say, the Truck takes X hours to finish the distance of D miles.
Then X = D/45
(Hrs = Miles / Miles/Hr)
Also, say the car takes Y hours to travel the same distance D.
Then Y= D/60
Then Y (hrs) = D (miles)/ 60 MPH
We also know the truck travels 2 hrs longer.
Thus X=Y+2
Putting all together,
D/45= (D/60)+2
or,
(4D-3D)/180 = 2
Thus D=360 miles.
Then the truck travelled, X hrs = D/45 = 360/45 = 8 hrs.
And the car travelled,
Y=D/60 = 360/60=6 hrs.
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kanchu!
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Posted on 03-31-11 12:23
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Always calculate interms of D=RxT!
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syanjaali
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Posted on 03-31-11 12:58
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After hours of घोत्ल्याइ and your answer give me idea , Can we do this way? x for truck and y for car.
As per Stiffer , 45x=60y
x= y+2
45 x - 60y = 0
x - y = 2
--------------------------
For American High School children have to be simplest way ( they can not understand certain math).
Last edited: 31-Mar-11 01:09 PM
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Stiffler
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Posted on 03-31-11 1:03
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While they are in equation form, I thought my answer would be more easier to understand, no?
By the way, the second equation is wrong.
X=y+2 (truck travels 2 hrs longer).
Thus X-Y=2 (not -2)
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syanjaali
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Posted on 04-01-11 3:05
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Thank you all for your input. Student liked the way Stiffer explained, higher grade with math interest student liked NAS, I thought I came wth the simplest form , without explanation , just did as I did to pass the EXAM.
Thank you agian.
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