what answer do you get????????

Question

i have worked it out but im not if its right so i just wanna see wat everyone else gets...this is da question!

Craggy point lighthouse flashes every 25 seconds and devils rock lighthouse flashes every 40 seconds. If they flash together how soon will it be before they flash together again??????????????

gd luck

Answer 1

200 secs (i think)

Answer 2

After they flash together, Craggy point flashes after 25 secs, then Devils at 40 secs, then Craggy at 50 secs, then Devils at 80. But still not together yet. You could carry on this way, but it's a bit boring.

The quickest way is to think what the first number is that both 25 and 40 fit into. The multiples of 40 are 40, 80, 120, 160, 200... and you can see that 200 is the first multiple that 25 fits into as well.

Therefore 200s is the answer.

Answer 3

You find the Lowest Common Multiple of 24 and 40 which is 200. So the lights flash together again after 200 seconds or 3 minutes 20 seconds.

Answer 4

what u need is the lowest common multiple (LCM) of 25 and 40. 25 = 5 X 5 and 40 = 5 X 8 so their common factor is 5 and uncommon factors are 5 and 8 so the LCM = 5 X 5 X 8 = 200, so the two lighthouses will flash together every 200seconds once. Hope that helps.

Answer 5

200 seconds...

Craggy point will flash at 25, 50, 75, 100, 125, 150, 175 and 200 seconds
Devils rock will flash at 40, 80, 120, 160, 200 seconds

200 is the first time the flashes coincide.

Answer 6

You take the longest time which is 40s and multiply it by 1 then 2, 3 4, etc until you reach a number that can be exactly divided by 25 the shortest time. so look at the multiples we have 40, 80, 120 ,160, and 200. 200 /25= 8 exactly.
Therefore the lights synchronise every 200s

Answer 7

You are supposed to get the LCM which is the Lowest Common Multiple for 25 and 40 is = 5 x 5 x 8
= 200 sesconds

Answer 8

200

Answer 9

After 200 sec

Answer 10

200 seconds

Answer 11

200 seconds