Q. 64.2( 80 Votes )
The traffic lights at three different road crossings change after every 48 seconds, 72 seconds and 108 seconds respectively. If they change simultaneously at 7 a.m., at what time will they change simultaneously again?
Time-period after which these lights will change = LCM of 48, 72 and 108
LCM is the lowest common multiple. LCM of two numbers It is the smallest number that is divisible by both of them.
LCM = 2 × 2 × 2 × 2 × 3 × 3 × 3 = 432
The lights will change together after every 432 seconds.
60 seconds = 1 minute
432 seconds = 432/60 min
= 7 minutes and 12 seconds
Total time will be 7 am + 7 min + 12 sec.
Hence these lights will change simultaneously again at 7:07:12 am.
Rate this question :
LCM of 10, 15 and 20 isNCERT - Exemplar Mathematics
Determine the greatest 3-digit number exactly divisible by 8, 10 and 12.NCERT - Mathematics
Find the LCM of the following numbers in which one number is the factor of the other:
(a) 5, 20 (b) 6, 18
(c) 12, 48 (d) 9, 45
What do you observe in the results obtained?NCERT - Mathematics
Find the smallest 4-digit number which is divisible by 18, 24 and 32.NCERT - Mathematics
Three boys step off together from the same spot. Their steps measure 63 cm, 70 cm and 77 cm respectively. What is the minimum distance each should cover so that all can cover the distance in complete steps?NCERT - Mathematics
The LCM of two or more given numbers is the lowest of their common_____.NCERT - Exemplar Mathematics
The LCM of two coprime numbers is equal to the product of the number.
The LCM of two numbers is greater than the larger of the numbers.