Kaplan Bells

[singhsa]

Came across this question in CAT6 from Kaplan 2009 CD.

A certain assembly line celebrates every finished car by ringing a bell a number of times equal to the number of cars finished so far that day. The time required for each ring is exactly equal to the time interval of silence between rings. For the 5th car finished, the time lapse between the beginning of the first ring and the end of the last ring is 27 seconds. For the 12th car finished, how many seconds elapse between the beginning of the first ring and the end of the last ring?

1. 33
2. 36
3. 66
4. 69
5. 70

Could'nt make head or tail of the explanation provided. Please help

OA - 69

[garudcvg]

Bell 1 - n seconds
Bell 2 - n seconds
Silence between the two ringing bells 1 and 2 = n
Which means for 5 ringing bells total time is 5n + 4n(silence time) = 9n = 27 i.e n = 3
now the 12th car is finished so we have 12n ringing time + 11n silence time = 23n = 23 X 3 = 69 seconds

Hope this helps..

[singhsa]

Bell 1 - n seconds
Bell 2 - n seconds
Silence between the two ringing bells 1 and 2 = n
Which means for 5 ringing bells total time is 5n + 4n(silence time) = 9n = 27 i.e n = 3
now the 12th car is finished so we have 12n ringing time + 11n silence time = 23n = 23 X 3 = 69 seconds

Hope this helps..

Thanks. I think I had difficulty interpreting the question.