1. 11 hours after A and B had started working, 45 percent of the work was still remaining.

Knowing the combined rate of work alone, we cannot clearly tell how much of the work they do separately.

Hence it is not possible to find out how long would it take A to do the work on his own.

The only information it would take for them

220/9 hours to complete the work.(Insufficient)

2. After the work was completed, it was found that A had done 60 percent of the work.

If A had done 60% of work, B would have done the other 40% of the work.

However, not knowing the time they would take to complete the work,

we will not be able to tell how much time A would take to complete the work (Insufficient)

On combining the information presented in both the statements,

we have the time taken for both of them to complete the work and the percentage of work A does.

So we can find out how much work A does in an hour, with which we can how much time he takes to complete the entire work(Sufficient)

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