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aditi2013
Dear all,

I have read the answer to this question but I am still confused. Does someone have an easier way to solve this problem?

Q: A museum offers four video programs that run continuously throughout the day, each program starting anew as soon as it is finished. The first program runs every 15 minutes, the second every 30 minutes, the third every 45 minutes, and the fourth every 40 minutes; the first show of each program starts at 10am and the last showing of each program ends at 4 pm. If a tour group can watch the programs in any order, but needs at least ten minutes between programs to regroup, what is the least amount of time the group can take to watch all four programs?


A.165 mins
B.164 mins
C.160 mins
D. 158 mins
E. 157 mins

First notice the minimum amount of time that needs to be taken: 15+10 + 30+10 + 45+10 + 40 = 160 mins
So D and E are out.
Since all show timings are a multiple of 5 and the group needs 10 mins to regroup, there is no way we will get 164. Hence the only options that will work out are 165 or 160.
If 160 is the answer, we have no wriggle room. We must watch shows one after the other with only 10 mins in between.

Shows: 15 mins, 30 mins, 40 mins, 45 mins
If we start with 15 min show and then regroup in 10 mins, we need to start another show in 25 mins. But no show starts in 25 mins so let's not start with 15 mins. (Same logic can be used to show that we cannot watch 40 min and 45 min shows first if we want to spend a total of only 160 mins)

If we start with 30 min show and then regroup in 10 mins, we need to start another show in 40 mins. A show does start in 40 mins so let's watch that. Now 80 mins have passed. We take 10 mins to regroup and now 90 mins have passed. Both the other shows start now. We watch the 45 min show and regroup for 10 mins. Now 145 mins have passed. But the 15 min show will start in 5 mins so we will need to wait another 5 mins for it and then watch it.
Total time taken will be 165 mins.

We cannot watch all the shows in 160 mins.

Answer A

Hey great Karishma!!
I took 6 mins to solve... but still got it wrong as 160 mins...
I wrote all possible combinations...

Didnt even think i can eliminate D E and B so easily until i see ur solution
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aditi2013


Karishma u are great..finally after breaking my head, i got it..is this a 700 level Q and can it be solved in 2 mins on the D-day?

The question isn't hard.. more like tedious. You need to work through the options to figure out that 160 is not possible. That could be time consuming. You can do it in 2 mins if you stay focused (which is hard to do under exam time constraints). So possibly you might end up spending more time on it.
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VeritasPrepKarishma
aditi2013


Karishma u are great..finally after breaking my head, i got it..is this a 700 level Q and can it be solved in 2 mins on the D-day?

The question isn't hard.. more like tedious. You need to work through the options to figure out that 160 is not possible. That could be time consuming. You can do it in 2 mins if you stay focused (which is hard to do under exam time constraints). So possibly you might end up spending more time on it.


Ya its hard in exam to stay focused on time...
hmm thanks for this question...
Looking forward more challenging questions to learn :)
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aditi2013
A museum offers four video programs that run continuously throughout the day, each program starting anew as soon as it is finished. The first program runs every 15 minutes, the second every 30 minutes, the third every 45 minutes, and the fourth every 40 minutes; the first show of each program starts at 10am and the last showing of each program ends at 4 pm. If a tour group can watch the programs in any order, but needs at least ten minutes between programs to regroup, what is the least amount of time the group can take to watch all four programs?

A. 165 mins
B. 164 mins
C. 160 mins
D. 158 mins
E. 157 mins

oh damn..took some time to solve this one...got with the below best option:
start with the second movie, finish at 10:30. 10 mins pause, next movie starts at 10:40, the fourth one. 4th finishes at 11:20. another 10 mins pause. 11:30. at 11:30 starts the 3rd showing of the third movie. so at 12:15 finishes the 4th one. 10 mins pause. 12:25. well, we have to wait for another 5 mins while the last one (first) starts at 12:30. then more 15 mins to watch the first one, and finish at 12:45. total 2h45m. in minutes, 165. A
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A museum offers four video programs that run continuously throughout the day, each program starting anew as soon as it is finished. The first program runs every 15 minutes, the second every 30 minutes, the third every 45 minutes, and the fourth every 40 minutes; the first show of each program starts at 10am and the last showing of each program ends at 4 pm. If a tour group can watch the programs in any order, but needs at least ten minutes between programs to regroup, what is the least amount of time the group can take to watch all four programs?

A. 165 mins
B. 164 mins
C. 160 mins
D. 158 mins
E. 157 mins

We see that all the running time of the programs and break time between the programs are a multiple of 5, thus the answer must be a multiple of 5. This allows us to eliminate choices B, D and E.

Since we have to wait at least 10 minutes between the programs. We can watch the second program (30 minutes) at 10 am first and when it finishes at 10:30 am, we can just wait exactly 10 minutes to watch the fourth program (40 minutes) which starts 10:40 am. It finishes at 11:20 am and we wait again exactly 10 minutes and at 11:30 am, we have two choices: either watch the first program (15 minutes) or the third program (45 minutes). Let’s analyze each option.

If we watch the first program at 11:30 am, it finishes at 11:45 am and we have to wait 30 minutes to watch the third program at 12:15 pm. It finishes at 1 pm, so the 4 programs including the breaks take exactly 3 hours (10 am to 1 pm) or 180 minutes. Notice that 180 minutes is not one of the choices.

Now let’s say we watch the third program at 11:30 am, it finishes at 12:15 pm and we just have to wait 15 minutes to watch the first program at 12:30 pm. It finishes at 12:45 pm, so the 4 programs including the breaks take exactly 2 hours 45 minutes (10 am to 12:45 pm) or 165 minutes.

Answer: A
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