Question

A and B working together they can complete in 8 days and A alone can complete that work in 12days then B alone can do that work in how many days. b) 12 days a) 24 days c) 16 days d) 20 days​

Answer 1

B alone can complete it in 12 days therefore in 4 days he can do 1/3 of it and in 8 days he can complete 2/3 of total work => A can complete 1/3 of the total in 8 days(since 2/3 B will do)

B worked for 4 days => 1/3 completed

And remaining is 2/3

So A will take 16 days to complete the rest

(8 days-> 1/3

hope it is helpful

16 days -> 2/3)

Answer 2

Answer:

A and B working together they complete in 8 days.

so, A+B= 8 days

Alone A can complete work in 12 days

To find B alone can do that work in How many days :-

$\sf \: (A+B)'s \: \: one \: \: day's \: \: work = \frac{1}{8} \\ \\ \sf (A )'s\: \: one \: \: day's \: \: work \: = \frac{1}{12} \\ \: \\ \sf \: (B )'s\: \: one \: \: day's \: \: work \: = \frac{1}{8} - \frac{1}{12} \\ \sf \: = ( \frac{1 \times 3 - 1}{24} ) \\ \\ \sf \: = ( \frac{3 - 1}{24} ) \\ \\ \sf \: = \cancel \frac{2}{24} \\ \\ \sf \: = \frac{1}{12} \\ \\ \sf(B )'s\: \: one \: \: day's \: \: work \: = \frac{1}{12}$

therefore, alone B will complete that work in 12 days.

HOPE IT HELPS YOU DEAR... :)