A,B,C can do a piece of work in 20days, 30days and 40days respectively, working alone. How soon can the work be done if A is assisted by B and C on alternate days? Choose one:
A) 3days
B) 1day
C) 5days
D) 10days
E) 7days
3days+B 1day work = 1/20 + 1/30  +  1= 
<gadget id="calculator"> +  1</gadget>
<output>1</output>
1/20 + 1/30= 1/12   3days+C 1day work = 1/20 + 1/40  +  1= 
<gadget id="calculator"> +  1</gadget>
<output>1</output>
1/20 + 1/40= 3/40   work done in 2 days = 1/12 + 3/40 = 19/120   19/120 work is done by 3days in 2days   Whole work will be done in 2*19/120 = 3days approximately   3daysnswer is 3days
<result>A</result>
A,B,C can do a piece of work in 20days, 30days and 40days respectively, working alone. How soon can the work be done if A is assisted by B and C on alternate days?