Question

The total stopping distance T of a vehicle is shown below, where T is in feet and x is the speed in miles per hour.
T = 6.5x + 0.5x2
Approximate the change and percent change in total stopping distance as speed changes from x = 20 to x = 25 miles per hour. (Round your answers to one decimal place.)

Answer 1

Our value when x=20 is equivalent to
T = 6.5*20+0.5*20^2 (I assume this final 2 is an exponent)
Which is equal to: 330

Answer 2

However, our value when x=25 is equivalent to
T = 6.5*25+0.5*25^2 (Once again, this answer depends on whether or not the final 2 is an exponent. I'm not sure, so let me know.)
Which is equal to: 475

Answer 3

yes the final 2 is an exponent

Answer 4

Ok great, so our change is equal to 475-330, which is 145.

Answer 5

And our percent change is (145/475)*100, which is approximately a 31% increase.

Answer 6

The answer is suppose to be 40.2 percent according to my review sheet

Answer 7

What did we do wrong

Answer 8

Very sorry, I made a mistake in calculating percent increase.

Answer 9

thats okay! Do you know where you made a mistake at?

Answer 10

How to calculate percent change: http://www.skillsyouneed.com/num/percent-change.html
So what should our percent change be?

Answer 11

I figured out where I went wrong! Our percent change is equivalent to the ratio of the two values multiplied by 100. So, the percent change is (475/330)*100, which is 140.2% change or a 40.2% increase.

Answer 12

(475/330)*100 is 143.9 percent change or 44.9 percent change. thanks for your help though

Answer 13

I'm sorry, I'm not sure what I'm doing wrong.