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Home Q & A Board Science-Related Homework Help Physics
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microman microman
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11 years ago
For a car moving at a constant speed, the distance traveled varies directly with the time spent driving. If such a car travels 220 miles in 4 hours, how long does it take to travel 385 miles?
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wrote...
#1
11 years ago
7 hours
wrote...
#2
11 years ago
Hi,

7 hours <==ANSWER

220 . . 385
------ = ------
 4 . . . . x

220x = 4(385)

220x = 1540

 x = 7

I hope that helps!!
wrote...
#3
11 years ago
4 hours = 220 miles

How many hours does it take to go one mile? = 4 / 220

Now multiply that by 385 to get how many hours it takes to go that far.

Then use the decimal portion of the answer and multiply it by 60 to get minutes.

Then use the decimal portion OF THAT and times it by 60 to get seconds (if any).
wrote...
#4
11 years ago
7 hours. you do 220 divided by 4 to find out the distance per hour (55 mph). Then you do 385 divided by 55 to find 7 hours.
wrote...
#5
11 years ago
Figuring out from the already given statistics, it travels 220 miles in four hours, that means it's going at a rate of 55 miles per hour. 385 miles/ 55 = 7 hours.
wrote...
#6
11 years ago
Since the distance traveled varies directly as the time spent driving, we have that:
D = kt, where D is the distance, k is a constant, t is the time spent driving.

Since D = 220 when t = 4:
220 = 4k ==> k = 55.

So, the equation that relates D and t is:
D = 55t.

When D = 385:
385 = 55t ==> t = 7 hours.

I hope this helps!
wrote...
#7
11 years ago
Since speed is constant. you can find speed using the first two givens (220miles and 4 hours)
distance: 220 miles
time: 4hours
speed = distance/time
         = 220/4
         = 55miles/hr
and if you traveled 385 miles
distance: 385 miles
speed = 55miles/hr
time = distance/speed
       = 385/55
       = 7hrs
Answer: 7 hours!
wrote...
#8
11 years ago
to solve this, you can make a proportion. it will be: miles/hours =miles/hours

so: 220/4=385/x  (x is the number of hours you are looking for)
-use cross product and get:
220x=385(4)
220x=1540 (divided by 220)
x=7
7 hours is you answer
wrote...
#9
11 years ago
Use this formula to find that:
Rate of travel (R) * Time of travel(T) = Distance traveled(D)

We don't get the rate of travel, but we get the time and distance. That allows us to find the rate w/ this equation.

R*4 = 220
R = 55

now, we plug that value and the new distance to get our new time.
55*T = 385
T = 7

It takes 7 hours to travel 385 miles at a constant speed of 55mph.

Hope that helps!
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