At 6'o clock clock ticks 6 times. The time between first and last ticks was 30sec. How much time it takes at 8'o clock.  Pick.
A) 54 sec	B) 48 sec	C) 42 sec	D) 70 sec	E) 60 sec

Rationale: at 6 ' 0 clock , clock ticks 6 times . so , there must be 5 intervals between clock ticks . time between first and last ticks = 30 sec so , 1 interval = 30 / 5 = 6 sec so 6 ' o clock 5 * 6 = 30 sec 7 ' o clock 6 * 6 = 36 sec 8 ' o clock 7 * 6 = 42 sec so , 42 sec at 8 ' o clock . answer : c
Answer: C