Question

B takes 6 days less than what A takes to complete the same work . Working together A and B take 7 1/5 days to complete the work.In how many days A alone can do the work?​

Answer 1

Answer:

18

if A takes X days then in one day A will do 1/X work

then B will take x-6 days to complete the work so he will do 1/x-6 work

the work is completed in 36/5 days so in one day 5/36

so 1/x+1/x-6= 5/36

2x-6/x^2-6x= 5/36

72x-216=5x^2-30x

5x^2-102x+216= 0

using b^2-4ac

10404- 4320

√d=78

102+ 78/10 (as day can't be negative)

18 = number of days A take to do the work