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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
Hi Brent, if I calculate with
B's speed = 240/ B-5
T's speed = 240/B + 4
240/ B-5 = 240/B + 4
240/ B-5 = (240 + 4B)/B
240B = (B-5)(240 + 4B)
240B = 240B + 4B^2 -1200 -20B
4B^2 -20B -1200 = 0
B - 5B - 300 = 0
(B-20) (B+15)=0
B = 20 , -15
I'm having a hard time
I'm having a hard time following your solution.
If B = Bill's speed, then B + 5 = Ted's speed (since Bill's speed was 5 mph slower than Ted's speed, we can also conclude that Ted's speed was 5 mph greater than Bill's speed).
Are you letting B = Ted's speed?
Also, when you wrote "B's SPEED = 240/ B-5" did you mean Bill's travel TIME?
Since you got B = 20 mph as your answer, I'm assuming you have actually found Ted's speed, which would mean Bill's speed is 15 mph.
I suggest you try solving the question again, but be very careful with how you define speeds and times.
My bad Brent. Let me calrify
T's speed = S
B's speed = S - 5 (since Bill's speed was 5 mph slower than Ted's speed)
T's time = 240/S + 4
B's time = 240/ S-5
240/ S-5 = 240/S + 4
240/ S-5 = (240 + 4S)/S
240S = (S-5)(240 + 4S)
240S = 240S + 4S^2 -1200 -20S
4S^2 -20S -1200 = 0
S^2 - 5S - 300 = 0
(S-20) (S+15)=0
S = 20 , -15
B's speed = S - 5 = 20-5 = 15
Perfect. Nice work!
Perfect. Nice work!
Brilliant thanks Brent for
One last question to clarify as noticed that your final answers are 15,-20 but mine are (20-5 = 15), -15.
Is there any issue with it and not sure why are they different? Thanks Brent
The differences in our
The differences in our solutions are caused by the fact that I created and solved an equation involving Bill's speed B, whereas you created and solved an equation involving Ted's speed S.
Got it thanks 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!
Question link: https:/
Hi Brent, can you please share your solution for this question?
Here's my full solution:
Here's my full solution: https://gmatclub.com/forum/each-type-a-machine-fills-400-cans-per-minute...
Hi Brent,
I struggled with the arithmetic approach so I decided the go with the Put-in numbers approach, starting with C.
So, if RateB= 12 then TimeB must be 20h, ergo TimeT must be 16h. If we check 240/16, that equals RateT to be 15. RateB-RateT=3 =/= 5. Eliminate answer C.
Then I went for an easy integer such as the one found in answer E to repeat the same operation, which is the correct answer.
My question is the following - how should I choose the next value after I discarded answer C.
Meaning, the difference between Rates in answer C was 3 (not 5 as the statement says) but I really did not know whether to choose a smaller value (for instance that of answer B) or to choose a bigger value (for instance answer E).
Thank you.
Here's the key concept at
Here's the key concept at play here.
Notice that, the closer bills speed gets to 5 mph,the greater the RELATIVE speeds between the two people.
For example, if Bill's speed = 6 mph, then Ted's speed is 1 mph, which means Bill's speed is SIX TIMES that of Ted's speed.
For example, if Bill's speed = 10 mph, then Ted's speed is 5 mph, which means Bill's speed is TWO TIMES that of Ted's speed.
For example, if Bill's speed = 25 mph, then Ted's speed is 20 mph, which means Bill's speed is 1.25 TIMES that of Ted's speed.
Now let's test answer choice C:
If Bill's speed = 12 mph, then Ted's speed is 7 mph, which means Bill's travel TIME is 20 hours and Ted's travel time is about 34 hours.
Since we need a time difference of only 4 hours, we want their relative speeds to be closer to each other.
As such, we need their speeds to be greater.
So, we can eliminate answer choices A, B and C
Does that help?
Can I get the solution for
https://gmatclub.com/forum/working-simultaneously-at-their-respective-constant-rates-m-143705.html
Here you go: https://gmatclub
Here you go: https://gmatclub.com/forum/working-simultaneously-at-their-respective-co...
Here you go: https://gmatclub
Here you go: https://gmatclub.com/forum/working-simultaneously-at-their-respective-co...
and the solution for this
https://gmatclub.com/forum/during-a-trip-francine-traveled-x-percent-of-the-total-distance-at-an-94933.html
Here's my solution: https:/
Here's my solution: https://gmatclub.com/forum/during-a-trip-francine-traveled-x-percent-of-...
Can I get the solution for
https://gmatclub.com/forum/a-pump-started-filling-an-empty-pool-with-water-and-continue-73138.html
You bet. Here's my full
You bet. Here's my full solution: https://gmatclub.com/forum/a-pump-started-filling-an-empty-pool-with-wat...