A and together we can complete a task in 7 days. can do it alone in 20 days. What part of the work was carried out by ?

I.A completed the job after and worked together for 5 days.

II.Part of the work done by could have been done by and together in 6 days.

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I alone is sufficient while II alone is not sufficient to answer.

II alone is sufficient while I alone is not sufficient to answer.

Either I or II alone sufficient to answer

Both I and II are not sufficient to answer.

answer is A.

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Detailed Solution

Concept- In order to answer this issue, we must identify the portion (or portion) of the task that A alone completed such that A and B could only collaborate for five days. For this, we'll employ the unitary technique and the idea that the sum of the labour done by each worker in a day equals the overall work performed in a day.
Let A and B finish the job each working alone, respectively, as A and B.
The answer to the question is that A and B collaborate to do a task in seven days. As a result, the daily workload for A and B is stated as follows:

From part I of the question,

and

worked together for 5 days so, the work completed in 5 days by

and

is given as
Question Image

As, the total work is denoted by 1 so, the remaining work that has to be done by A alone is given as Question Image

.
Hence,

of the total work is done by A alone after B left the job after 5 days.
Therefore, part I is adequate to respond to the query.
The work that was finished by A may have been accomplished by B and C together in 6 days, according to part II of the question, but since we have no additional relationships with the variable C, we are unable to establish the work that C and consequently A completed.
As a result, section II is in no way adequate to provide a response.
I by myself is therefore sufficient, whereas II by myself is not.
Hence, the answer is option 1.
Syllabus: CBSE

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