A, B and C can do a job working alone in 50, 75 and 20 days respectively. They all work together for 4 days, then C quits. How many days will A and B take to finish the rest of the job?
LCM of 50,75 an 20 is 300 units
Each day A can do 300/50 =6 units
Each day B can do 300/75 =4 units
Each day A can do 300/20 =15 units
In each day 6+4+15=25 units
for 4 days they do 4*25=100 units
Each day AÂ and B an together do 10 units
Therefore 200/10 =20 days
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