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lalalemon93

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## Any Answers would be Greatly appreciated!

! Lisa drove 100 miles, then increased her speed by 25 miles per hour for 225 miles. If the second part of the drive took 1 hour longer than the first part, find her average speed.

This open post was written 1 year, 10 months ago | V/U/S: 525, 13, 3 | Edit Post | Leave a reply | Report Post

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### Replies (13)

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just start plugging numbers in. I just guessed a random number and I got it right on the second try.

First I tried 1 mile per hour for the first 100 miles. That didn’t make sense. Then I tried a bigger number…

How did you do it? Can you explain it?

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So you came up with?

Help me with: Missing Network Adaptor!

If you could tell me the way the equation is supposed to be set up, I can figure it out. Thats what im having trouble with.

Help me with: Missing Network Adaptor!

Let’s guess 20 miles per hour for the first 100 miles. It would take her five hours to go that far, thats easy. If she increased it by 25 (now she’s going 45), how long would it take her to go 225? More than just one hour longer. Then 20 is too small. So big a bigger number.

I did trial and error. obviously its going to end up being your total miles divided by your total time.

the one thing you know is the total miles: 325. Maybe if you let the average speed be x and the total time be y??

Would it be 65?

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It turned out to be 65. Thanks for your help!

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im trying to figure out what the equation would be now. Because I figured the answer would end up being 325miles divided by five hours. Which ends up being 65. But what would it look like without trial and error?

the mathematic way was a headache…
it is easier done by logic, but i tried the math way…:
(which there is probably a better way anyhow, but that’s what i scratched from the bacl of my mind…)

v1 = 100/t1
v2 = 225/t2

t2=t1+1
v2=v1+25

>>>

100/t1 + 25 = 225/(t1+1) (calling t1 “t” hence forth)

100/t + 25 - 225/(t+1) = 0 [/25]

4/t + 1 - 9/(t+1) = 0 [*(t+1)]

(4t+4)/t + t + 1 -9 = 0 [*t]

4t+4+t^2-8t = 0

t^2 -4t +4 = 0

(t+2)(t-2) = 0

t1 = 2

>>>>

total time:
T=5

325/5 = 65 = V (average speed)

did it help?

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