Question

3. A and B together can do a piece of work in 12 days while B alone can finish it in 30 days . in how many days can A alone finish the work?​

Answer 1

Step-by-step explanation:

B's 1 day work =1/30

A and B's 1 day work is 1/12

so

1/A+1/B=1/12

1/A+1/12=1/12

1/A=1/12-1/30

1/A=30-12/30×12

1/A=18/360

1/A=1/20

A=20

Answer 2

Answer:

20 days

Step-by-step explanation:

A can do a work in n days. Then A's one days work will be 1/n

Since A and B can do a job in 12 days,

∴1/A+1/B=1/12→1

But B can finish the work in 30 days.

∴  1/B=1/30 →2

Substituting 2 in 1 we get

⇒1/A+1/30=1/12

Taking 1/30 to the right side.

⇒1/A=1/12-1/30

⇒1/A=5-2/60 Taking LCM

⇒1/A=3/60

⇒1/A=1/20

therefore A alone can complete the work in 20 days.