Question

The traffic lights at three different road crossings change after every 72 seconds, 108 seconds and 132 seconds respectively. If they change simultaneously at 7.am, at what time will they change again simultaneously. ​

Answer 1

Answer:

Ncert solutions

Grade 6

Mathematics

Chapters in NCERT Solutions - Mathematics, Class 6

Exercises in Playing With Numbers

Question 1

Q6) 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?

SOLUTION:

to find the at what time the lights will change simultaneously we need to find the LCM of 48, 72 and 108

LCM of 42, 72 and 108

=2\times2\times3\times3\times2\times2\times3=2×2×3×3×2×2×3

432\div60\min\ =\ 7\min\ 12\ \sec432÷60min = 7min 12 sec

hence, the lights will again change simultaneously at 7mins 12sec past 7 am.

Answer 2

Answer:

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