Question

plzz solve this question 11

Answer 1

Hey dear !!!!

Here according to question traffic light on different road crossing change simultaneously after every 48 sec , 72 sec and 108sec

so take 1st lcm
we get

prime factor of 48 = 2×2×2×3×2
prime factor of 72 = 2×2×2×3×3
"""""""""""""""""""" 108 = 2×3×3×3 × 2

common term in three term is 2 ,3
and uncommon term 2×2×2×2×2×3×3×3×2

hence lcm will be

2⁴ ×3³

=> 432 means 432sec


=>432sec After 432 second it will change together

hence that time = 8 + 432sec

8hour + 432/60

= 8 hour + 7min + 2sec

hence

= 8 h 7min 2sec will be that time when those three traffic light will be change again simultaneously

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Hope it helps you !!

@Rajukumar111

Answer 2

Heya !!
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Given that the traffic light at 3 different road crossing change after every 48 seconds, 72 seconds and 108 seconds respectively.

48 = 2 × 2 × 2 × 2 × 3
= 2^4 × 3

72 = 2 × 2 × 2 × 3 × 3
= 2^3 × 3^2

108 = 2 × 2 × 3 × 3 × 3
= 2^2 × 3^3

L.C.M = 2 × 2 × 2 × 2 × 3 × 3

L.C.M = 2^4 × 3^3

L.C.M = 432

Hence, they will change after 432 seconds.

1min = 60 seconds.

432seconds = 7min 12 seconds.

Given that they change simultaneously at hour.

so, at 8hr 7min and 12 seconds they will change again.

Time :- 8hr 7min 12sec.
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Hope it helps..

Thanks :))