another tricky question

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aaman1
Posts: 35
Joined: Wed May 25, 2011 11:36 pm

another tricky question

Post by aaman1 »

Hi
Can anyone help with these qeustions:

TV 1 and TV 2 are televisions channels both showing films that start at 8:30 pm.
TV 1 puts on advertisements every 10 minutes after the start of a film.
TV 2 puts on advertisements every 15 minutes after the start of a film.
Q. What is the is earliest time that there will be advertisements on both channels at the same time?
answer 9:00pm
Q. If the shortest film ends after 2 hours, how many times (during the films) will advertisements appear on both channels at the same time?
answer 3
yoyo123
Posts: 8099
Joined: Mon Jun 18, 2007 3:32 pm
Location: East Kent

Re: another tricky question

Post by yoyo123 »

I always find a diagram helps !
svg123
Posts: 250
Joined: Thu Feb 24, 2011 1:34 pm

Re: another tricky question

Post by svg123 »

You need to think of common factors or 10 & 15.
So, they will meet 30mins after the program starts for the first time and in 2hrs period they will cross each other 3 times. 9.00pm, 9.30pm, 10.00pm
I hope I am correct.
xyzzy
Posts: 86
Joined: Mon Jul 25, 2011 8:38 am

Re: another tricky question

Post by xyzzy »

svg123 wrote:You need to think of common factors of 10 & 15.
Common multiples, not common factors. The common factor is 5. The common multiples are 30, 60, 90 which are what is wanted here.
yoyo123
Posts: 8099
Joined: Mon Jun 18, 2007 3:32 pm
Location: East Kent

Re: another tricky question

Post by yoyo123 »

still think a diagram would help...
svg123
Posts: 250
Joined: Thu Feb 24, 2011 1:34 pm

Re: another tricky question

Post by svg123 »

xyzzy wrote:
svg123 wrote:You need to think of common factors of 10 & 15.
Common multiples, not common factors. The common factor is 5. The common multiples are 30, 60, 90 which are what is wanted here.
Sorry, yes common multiple.
hermanmunster
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Location: The Seaside

Re: another tricky question

Post by hermanmunster »

How about a diagram?
mystery
Posts: 8927
Joined: Tue Jul 21, 2009 10:56 pm

Re: another tricky question

Post by mystery »

Well, maybe a number line with times on it? I guess that's a kind of diagram. But having said that it's a pretty easy one to do without writing anything down and in an exam it would be quicker not to.

What was tricky about it? :wink:
aaman1
Posts: 35
Joined: Wed May 25, 2011 11:36 pm

Re: another tricky question

Post by aaman1 »

Thanks everyone for helping.
Manana
Posts: 710
Joined: Wed Mar 09, 2011 3:22 pm

Re: another tricky question

Post by Manana »

I think this is a silly question as it doesn't allow for the adverts to actually take up any time! Surely if the adverts were on every 10 or 15 minutes, you'd need to allow for 2-3 minutes each advert break (unless it's Sky-then about 6!) which would mess the times up ;)
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