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A car goes 900 miles in 16 hours how long does it take to go 400 miles?

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5 Answers

Good explanation! 

I would set it up like this 

put miles on top and hours on bottom and set the two equal to each other

900 Miles   =    400 miles

16 hours             X hours 

and cross multiply!

900 X = 16 (400) 

Solve for X

To start off we need to figure out with the information given how fast this car is actually going and then we can apply that to the 400 miles. 

So what we do is take the 900 miles it traveled and divide it by 16 hours. This gives us the amount of miles it traveled every hour, in other words we get the miles per hour.


Now we just divide the 400 by the 56.25mph to get the amount of time it takes to travel that distance:

400mi/56.25mph=7.11 hours. Answer. (The miles unit cancels and what's left is the hours)

Hope this helps!

These questions are classic. They are a variant on the Two Cars Algebra problem. Just remember this formula: Distance = Velocity * Time Step 1) Plug in the numbers and put an "N" for your unknown variable: 900 = N * 16 Step 2) Do the easy math (PEMDAS) first: 900 = 16N Step 3) Solve for "N" by dividing both sides by 16: 900/16 = 16N/16 Step 4) Solved! Your answer should have been 56.25 = N Now we have the hidden number of 56.25. That is the velocity. Let's just use the same algebra equation again (Distance = Velocity * Time), except that now Time is the unknown variable: 400 = 56.25 * N 2) 400 = 56.25N 3) 400/56.25 = 56.25N/56.25 4) You can finish this one yourself. Here is a hint: Don't be frightened by a repeating decimal! Whether you use a vinculum or round up/down is up to your teacher. You could use a fraction but the units would not match, thus making it incorrect. I hope this was of help to you! If anybody has an easier way or any corrections, please feel free to post because I enjoy learning as well.
Assuming the speed is constant, then we can set this up in a ratio of the distance over time (miles/hours) 900 miles/16 hours = 400 miles/x hours Since we want to solve for x, multiply both sides by x: (x) (900 miles/16 hours) = 400 miles Now multiply both sides by 16 and divide by 900: x = (400)(16)/900 = 7.111 hours or 7 1/9 hours

This is a proportion problem.  Set up the proportion so that miles/hours equals miles/hours

900/16 = 400/x                     900 miles per 16 hours equals 400 miles per unknown number of hours

16x(900/16) = 16x(400/x)      Cross multiply (multiply each fraction by both denominators)

900x = 6400                          Simplify

900x/900 = 6400/900              Divide each side by 900

x = 64/9                                 Simplify the fraction

It will take about 7.11 hours or 7 hours and 7 minutes.