Question

(a) Six bells commence tolling together and toll at intervals of 2, 4, 6, 8, 10
seconds respectively. After how many minutes will they toll together again
(i) 5 minutes
(ii) 6 minutes​

Answer 1

Answer : None of these options are correct.

They will hit again after 7 minutes and that is equal to 420 seconds

Step-by-step explaination :

1) 2 + 4 + 6 + 8 +10 = 30 seconds or 0.5 minute

2) 30 + 12 + 14 +16 + 18 + 20 = 110 seconds or 1 minute 50 seconds

3) 110 + 22 + 24 + 26 + 28 + 30 = 240 seconds or exactly 4 minutes.

4) 240 + 32 + 34 = 306 seconds or 5 minutes 6 seconds. ( Exceeding 5 minutes. Hence no. 1 option is not correct .)

5) 306 + 36 + 38 = 380 seconds or 6 minutes 20 seconds. ( Exceeding 6 minutes. Hence no. 2 is also incorrect.)

6) 380 + 40 = 420 seconds or exactly 7 minutes.

Hence, both options are wrong.

Really, asked a good question. Quite confusing.

Hope this answer helps you.