Question 164395
To find the average speed, divide the total miles by the total hours.

D = distance

r = rate = speed

t = time (in hours)

(82) Driving marathon. Felix drove 800 miles in x hours on Monday.

(a) Write a rational expression for his average speed.

Let D = 800

Let t = hour = x in your question

Then we have this:

800 = rx

We divide both sides by x to express the average speed.

800/x = r....Notice that 800/r is a rational expression.  The word rational means fraction.

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(b) On Tuesday he drove for 6 hours at the same average speed. Write a rational expression for his distance on Tuesday.

Here we are searching for distance.

Let D = distance

Let r = rate = speed

Let t = time (in hour) = x

D = xr

D = 6r....This is not a rational expression.  At the beginning of your question we read "Answers could be rational expressions." This means if they could be rational, they could also not be rational. This is the case for part (b).

D = 6r is a linear equation not rational.

Get back to me if you have any questions about my reply.