# Thread: heh heh need help in Pri 4 maths....

1. ## heh heh need help in Pri 4 maths....

been trying to figure this one out for the last few hours without success..... google here and there also no help...... been a long week and brain is fried from work..... so I'm mathematically challenged tonight ha ha

I'm almost a nervous wreck and brain cannot take this torture any more......

There were 3 alarm clocks in the room.
The 1st clock beeps every 12 mins
The 2nd clock beeps every 8 mins
The 3rd clock beeps every 6 mins
If they first beeped together at 7am, what time would they beep together again ?

If u know how to get the answer show the workings too ha ha ha

2. ## Re: heh heh need help in Pri 4 maths....

7:24am?

1st clock: 7:00, 7:12, 7:24
2nd clock: 7:00, 7:08, 7:16, 7:24
3rd clock: 7:00, 7:06, 7:12, 7:18, 7:24

to solve it mathematically, just find the lowest common multiple of the three intervals.

or is there a trick somewhere? hahaha

3. ## Re: heh heh need help in Pri 4 maths....

Oh... LCM question...

Here goes:
LCM of 12, 8, 6 = 24

Therefore, if starting time is 7am, the next time they beep together will be 7.24 am.

Cheers!

LCM is Lowest Common Multiple.

Multiple of 12 is 12, 24, ...
Multiple of 8 is 8, 16, 24, ...
Multiple of 6 is 6, 12, 18, 24, ...

4. ## Re: heh heh need help in Pri 4 maths....

My brain just stalled looking at this

5. ## Re: heh heh need help in Pri 4 maths....

i worked on the 2 min interval between the 6min beep and 8min beep clocks and 4 min interval between the 8min beep and the 12min beep clocks

got to 60min and 120mins and dunno if ans should be 9am ?

6. ## Re: heh heh need help in Pri 4 maths....

Originally Posted by zapline
Oh... LCM question...

Here goes:
LCM of 12, 8, 6 = 24

Therefore, if starting time is 7am, the next time they beep together will be 7.24 am.

Cheers!

LCM is Lowest Common Multiple.

Multiple of 12 is 12, 24, ...
Multiple of 8 is 8, 16, 24, ...
Multiple of 6 is 6, 12, 18, 24, ...
7am, 7.06am, 7.18am, 7.24am
7am, 7.08am, 7.16am, 7.24am
7am, 7.12am, 7.24am

oh yah hor !!!!! wah lau....... no wonder my 9 year old laughing at me all night

ok thread closed !!!

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