Mansoor50 wrote:
workout wrote:
GMATbuster's Weekly Quant Quiz#11 Ques #10
For Questions from earlier quizzes: Click HereMary and Jane working together can complete a task in 2 hours and 24 minutes. Jane and Karen working together can complete the same task in 1 hour 20 minutes whereas Karen and Mary working together can complete the task in 1 hour 30 minutes. Which of the following best represents the time (in minutes) taken to complete the task if Mary, Jane and Karen work together?
A)42
B)48
C)54
D)60
E)66
m+j= 144
j+k=80
k+m=90
adding gives:
2m + 2j + 2k = 314
m+j+k= 157
Can you explain where i am going wrong?
In this type of approach consider work done to be the LCM of three values
M+J= 144min
J+K=80 min
K+M= 90min
consider total work done to be 144
SO,
rate of M+J = 1 SINCE rate = work/time
rate of J+K = 1.8
rate of K+M =1.6
total rate equation will be
(M+J)+(J+K)+(K+M) = 1+1.8+1.6
2 ( M+J+K) = 4.4
(M+J+K) = 2.2
TOTAL WORK DONE = TOTAL RATE * TOTAL TIME
144 /2.2 = 65.45 approx 66 min
please let me know if i went wrong , if not, do consider kudos!