Harley1980 wrote:
joylive wrote:
A certain hall contains two cuckoo clocks. If the first clock chirps 20 times per hour and the second clock chirps 10 times per hour, and both clocks begin chirping at 1:15 PM, at what time will the first clock have chirped three times as many times as the second clock can per hour?
A. 1:24 PM
B. 2:05 PM
C. 2:30 PM
D. 2:45 PM
E. 4:15 PM
If we infer that cuckoo chirps evenly per time, than correct answer will be 9 minutes. Because first cuckoo chirps 1 time in 3 minutes and second 1 in 6 minutes.
So in 9 minutes first cuckoo shirps 3 times and second 1 time.
If we infer that cuckoo chirps 20 times once in hour than they will chirp simultaneously and this task has no solution:
1 hour 20:10
2 hour 40:20
an so on.
I reread solutions twice but can't understand why we infer that cuckoos chirp two times per hour and make equal number of sounds every half an hour?
Am I miss something?
Hi,
Your logic is absolutely correct but we are asked "at what time will the first clock have chirped three times as many times as the
second clock can per hour?"... per hour is the catch word..
second clock chirps 10 times in one hour... so the question is basically asking by when will the first clock chirp 30 times (thrice 10 chirps)..
first will take 1 hr 30 min for this ..
add it to 1:15.. ans 2 :45
ans D
hope it helped