A and B can do a work in 20days, B and C can do it in 30days; A,B and C together can finish it in 40days. A and C together will do it in?
Answers
A) 25days B) 30days C) 20days D) 15days E) 10days
A+B+C 1day work = 1/40   A+B 1day work + +  1= 
<gadget id="calculator">+ +  1</gadget>
<output>1</output>
1/40   A+B 1day work = 1/20   B+C 1day work  +  1= 
<gadget id="calculator"> +  1</gadget>
<output>1</output>
1/20   B+C 1day work = 1/30   A+C 1day work  +  1= 
<gadget id="calculator"> +  1</gadget>
<output>1</output>
1/30   A+C 1day work= 2*1/40 - 1/20+1/30 = 1/30   A and C together will do the work in 30 days.   Answer is 30days
<result>B</result>
A and B can do a work in 20days, B and C can do it in 30days; A,B and C together can finish it in 40days. A and C together will do it in?