This is an example of an intrinsic reward.
Intrinsic rewards are internal - they refer to feelings of accomplishment, of success, of pride, and are intangible, meaning that you cannot touch them. On the other hand, extrinsic rewards are actual objects that you receive as a reward for something you did.
Explanation:
20 men can do 1 W in 36 days
=> 20 men can do 1/36 W in 1 day
=> 10 men can do 1/72 W in 1 day.
30 girls can do 1W in 36 days
=> 30 girls can do 1/36 W in 1 day
=> 12 girls can do 1/90 W in 1 day.
Together 10 men and 12 girls can do 1/72 + 1/90 W in 1 day
= 9/360 = 1/40 W in 1 day.
Therefore they need 40 days to do the piece of work.
Copying my answer from this question from another student who asked the same one:
Social Darwinism is the belief that people and business are subject to the same laws of nature and natural selection. This has been used by business leaders, both in the Gilded Age and today, to create a belief that the strongest businesses are the ones that survive because they survive the competitive process of natural selection.
So, massive oil companies and railroad companies (and tech companies and banks today) used social darwinism to explain their rise to almost monopoly status as a "natural" thing that was accomplished merely using the laws of nature.
I would rate it (in my opinion) a 7/10!
