Concept:The law of diminishing marginal utility explains why a normal demand curve slopes downward.
Explanation:As a consumer takes more units of a good, the extra satisfaction from each additional unit falls.
This is diminishing marginal utility.
Because the extra satisfaction is lower, the consumer is willing to pay less for each additional unit.
Therefore, the quantity demanded rises only when the price falls.
This inverse relationship between price and quantity demanded gives a negative slope for a normal demand curve.
Answer:The law of diminishing marginal utility explains why the slope of a normal demand curve is negative.