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## Comment on

Bill and Ted in a Race## A the beginning of the video

Thanks

## Let's test one answer choice

Let's test one answer choice together.

B) 10

This means Bill's average speed is 10 miles per hour (mph).

Since Bill's speed is 5 mph slower than Ted's speed, we know that Ted's speed is 15 mph.

Travel time = distance/speed

So, Bill's travel time = 240/10 = 24 hours

Ted's travel time = 240/15 = 16 hours

So, we can see that Ted's travel time is 8 hours less than Bill's travel time.

These times do not match the information in the question, which says Ted's travel time is 4 hours less than Bill's. So, we need to check more answer choices.

## Once again! An excellent

## I'm glad you like it!

I'm glad you like it!

## Hi Brent,

Could you show me the step by step solution for this problem using double matrix method?

http://www.beatthegmat.com/ds-french-japanese-t222297.html

## The first solution here http:

The first solution here http://www.beatthegmat.com/at-least-100-students-at-a-certain-high-schoo... uses the Double Matrix method.

## From where did you got the

## I believe you're referring to

I believe you're referring to 3:13 in the video.

If so, we got 260 + 4B on the right side of the equation after we simplified the expression 240 + 4B + 20.

Does that help?

Cheers,

Brent

## i didn't get it. I fthe

If the average speed of Bill is slower, then the Speed of Bill = (Speed of Ted) - 5.

Right?

## I believe you're referring to

I believe you're referring to the point at 1:15 when I say that (Bill's speed) + 5 = Ted's speed.

This equation is EQUIVALENT to your suggested equation: Bill's speed = (Ted's speed) - 5

In fact, if we take your equation: Bill's speed = (Ted's speed) - 5

And add 5 to both sides to get: (Bill's speed) + 5 = Ted's speed, which is my equation.

Does that help?

Cheers,

Brent

## https://gmatclub.com/forum

please explain

## That question is not really

That question is not really GMAT-worthy.

Here's my full solution: https://gmatclub.com/forum/will-laurie-get-to-the-apartment-building-bef...

Cheers,

Brent

## https://gmatclub.com/forum/a

please explain

## Question link: https:/

Question link: https://gmatclub.com/forum/a-train-traveling-at-72-kmph-crosses-a-platfo...

Here's my solution: https://gmatclub.com/forum/a-train-traveling-at-72-kmph-crosses-a-platfo...

Cheers,

Brent

## This is my approach, but I

Givens:

240 = vb * tb = vt * tt

vb + 5 = vt

tt + 4 = tb

Solve for vb

vb * tb = vt * tt

vb * tb = (vb + 5) * (tb - 4)

vb * tb = vb * tb + 5tb - 4vb - 20

4vb + 20 = 5tb

4vb + 20 = 5 * 240/vb

vb^2 + 5vb - 300 = 0

(vb + 20) * (vb - 15) = 0

vb = 15

## Nice work!

Nice work!

## Add a comment