Question

A and B can do a job in 16 days and 12 days respectively. B
has started the work alone 4 days before finishing the job, A
joins B. How many days has B worked alone?
(a) 6 days
(b) 4 days
(c) 5 days
(d) 7 days
() None of these​

Answer 1

Answer:

He works only for 6days.

Step-by-step explanation:

Because 12-4 is 8days.

Answer 2

✤✤✤✤✤✤✤ Question ✤✤✤✤✤✤✤　

A and B can do a job in 16 days and 12 days respectively.

B has started the work alone.

4 days before finishing the job, A joins B. How many days has B worked alone?

(a) 6 days

(b) 4 days

(c) 5 days ✔✔

(d) 7 days

(e) None of these

✤✤✤✤✤✤✤ Solution ✤✤✤✤✤✤✤

time taken by A to do the job= 16 days

so,

work done by A in one day = 1 / 16

time taken by B to do the job= 12 days

so,

work done by B in one day = 1 / 12

Now

Let, total no. of days

for which B worked = x days

then,

total work done by B = x ( 1/12) = x /12

It is given that,

No. of days for which A worked = 4 days

then,

total work done by A = 4 (1/16) = 4/16=1/4

So,

( x / 12 ) + ( 1 / 4) = 1

taking LCM

( x + 3 ) / 12 = 1

cross multiplting

x + 3 = 12

x = 12 - 3

x = 9 days

Therefore,

total no. of days for which B worked = 9 days

so,

no. of days in which B worked alone = 9 - 4

no.of days for which B worked alone=5days

Therefore,

the correct answer of this question is

5 days.