The traffic lights at three different road crossings change after every 54 sec .63 sec. and 81 sec. respectively. After how many seconds the light will change simultaneously.

Question

The traffic lights at three different road crossings change after every 54 sec .63 sec. and 81 sec. respectively. After how many seconds the light will change simultaneously. (A) 9 min .15 sec (B) 18 min .54 sec (C) 21 min .9 sec (D) None

Tardigrade Admin · Accepted Answer

Interval of change =( L.C.M of 54,63,81) mathrmsec =3 × 3 × 3 × 3 × 2 × 7=1134 mathrmsec. <img class="img-fluid question-image" alt="image" src="https://cdn.tardigrade.in/img/question/mathematics/d6a0d20fc595d254002b0e2be80ef084-.png" /> So, the lights will again change simultaneously after every 1134 seconds i.e. 18 mathrm~min. 54 mathrmsec.

Q. The traffic lights at three different road crossings change after every $54 sec .63 sec$ . and $81 sec$ . respectively.
After how many seconds the light will change simultaneously.

$9 min .15 sec$

$18 min .54 sec$

$21 min .9 sec$

None

Interval of change $= ($ L.C.M of $54, 63, 81) sec$ $= 3 \times 3 \times 3 \times 3 \times 2 \times 7 = 1134 sec$ .

So, the lights will again change simultaneously after every 1134 seconds i.e. $18 min$ . $54 sec$ .

Q. The traffic lights at three different road crossings change after every 54sec.63sec. and 81sec. respectively. After how many seconds the light will change simultaneously.

9min.15sec

18min.54sec

21min.9sec