109. A and B can do a job together in 7 days. A is 1 times as efficient as B. The same job can be done by A alone in :

✅ The correct answer is option B.
(A’s 1 day’s work) : (B’s 1 day’s work) =
7
: 1   =   7 : 4.

4

Let A’s and B’s 1 day’s work be 7x and 4x respectively.

Then, 7x + 4x =
1
        11x =
1
        x =
1
.

7
7
77

A’s 1 day’s work =

1
x 7

=
1
.

77
11