This Is a Certified Answer

Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
Andy can do 1/18 th work  in a day.
Bill and Andy can do 1/10th work in a day.

So Bill can do in a day :  1/10 - 1/18 = 8/180 = 2/45 amount of work

Bill does only half day work.  So Now Bill does 2/45 * 1/2  = 1/45 th work each day.
Total work done now by Andy and Bill together = 1/45 + 1/18 = 7/90 in one day

They can complete work in 90/7 days = 12 + 6/7 days

Is mine wrong or yours wrong (which is probably impossible)?
sorry. there was arithmetic error
  • Brainly User
Rate of doing work = Work / Time taken. Let rate of doing works be A for Andy and B for Bill. Work W can be completed in following ways. W=A(18)=(A+B)(10). This says rate of working of B = A(4/5). This means B can complete a work in 22.5 days. But B works only for half a day, so rate of working of B is halved i.e. W=(B/2)(45). Now total time taken is W=(A+B/2)T. Solving this equation for T using the above ones you get T = 90/7 days