David watches Maria and Alma race electric trains around a track. Maria's train goes around the track in 10 seconds. Alma's train goes around the track in 12 seconds. How long will it take for both trains to cross the finish line together the first time?

A
30 seconds

B
60 seconds

C
72 seconds

D
120 seconds

60 seconds.

Step-by-step explanation:

We have been given that Maria train can go around the track in 10 seconds. Alma train can go around the track in 12 seconds.

To find the number of seconds after which both trains will cross the finish line together the first time we will find LCM of 10 and 12. LCM will give us the smallest positive integer that is divisible by both 10 and 12.  

Multiples of 10 are: 10, 20, 30, 40, 50, 60, 70,...    

Multiples of 12 are: 12, 24, 36, 48, 60, 72, 84,..  

We can see that least common multiple of 10 and 12 is 60, therefore, it will take 60 seconds for both trains to cross the finish line together the first time.

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step-by-step explanation:

step-by-step explanation:

the first 5 right here the next 5 i will upload as separate question