Final answer:
C can complete the work on their own in 12 days, compared to A's 10 days. A's daily work rate is 1/10 and C's rate is 1/12. Therefore, C's efficiency is about 83.33% compared to A's, meaning A is more efficient.
Step-by-step explanation:
The question involves finding out what is C's efficiency compared to A's when completing a work project. The scenario described is that A can complete work in 10 days, B in 15 days. They collaborate for 5 days, and then C finishes the remaining work in an additional 2 days.
Let's determine the work done by A and B in 5 days. Since A completes the work in 10 days, A's daily work rate is 1/10. Similarly, B's daily work rate is 1/15. Together, A and B's daily work rate is (1/10 + 1/15), which simplifies to 1/6 of the work per day. Over 5 days, they complete 5/6 of the work, leaving 1/6 of the work for C to complete.
Since C completes this 1/6 of the remaining work in 2 days, C's daily rate is (1/6) / 2, which is 1/12. This means C takes 12 days to do the whole job alone, which is slower than A, who takes 10 days.
To compare C's efficiency to A's, we look at their daily rates. If A's efficiency is considered to be 1 (since it's our baseline), we compare C's rate of 1/12 to A's rate of 1/10. C's efficiency relative to A's is therefore 10/12 or approximately 83.33%, meaning C is about 16.67% less efficient than A.