How to write a model in simplified from for the total time of the trips? and How long does the trip take when r is 4 mph?

Question

Sue travel 3 miles downstream in a kayak at a speed of r mph.She turns around and travels 4 miles upstream at a speed of 0.5r mph. Finally, you turn around and return to her original starting point t a speed of r+1 mph 

Answer 1

Kris, the key formula here is d=r*t, Distance (d) is equal to rate (r) times time (t). We have distance and rate (speed), so we want this formula in terms of time: t = d/r. So we need to divide the distance by the speed.

 

The first distance is 3 miles, and her speed is r mph, so we calculate t = d/r:

t = 3 / r

 

You can do the same for the second distance: t = d/r

 

For the third distance, you need to know the distance that she travels. Draw a picture of where she traveled, and identify how far she needs to go to return to her original starting point. Can you find t = d/r for this distance?

 

The total time of the trips will be the sum of each time. Since these use "r" as a variable, you'll have several fractions involving r. You may need to find the least common denominator and simplify this into a single fraction, depending on your teacher, course, or textbook.

 

Is there anything I can help clarify?