Question

Higher consumption of a commodity means lower and lower marginal utility, but total utility can never be negative. Do you agree?

Answer 1

Hint: 1) Total utility increases at a decreasing rate.
2) Negative total utility is an undesirable state.

Complete answer:
The amount the satisfaction that the consumption of a commodity provides is referred to as ‘utility’. There are two kinds of utilities that we know. They are total utility and marginal utility. When we consume something, for e.g. Object A, then our utility increases. It means that we get a high amount of satisfaction. In fact, it is the highest amount of satisfaction or utility when consuming Object A for the first time.
Total utility is the sum of all the utilities from all the consumptions. Hence, it is never negative.

Marginal utility on the other hand, is the addition in the total utility. It is the maximum at the first consumption and it keeps getting lower and lower as we consume more and more Object A.

The marginal utility and total utility are very much related to each other. Since the marginal utility keeps decreasing, there is a point when it reaches zero. At this point, where the marginal utility becomes zero, the total utility is at its peak. When we consume even more of
Object A after the marginal utility has reached zero, it starts going negative. When the marginal utility becomes negative, the total utility starts decreasing from its peak.

Note: We see that the increase in the total utility is equal to the value of the marginal utility at that level.
The value of the marginal utility always decreases and even goes negative.
Hence, the marginal utility implies that the total utility increases at a decreasing rate.