372. What change does a positive fraction undergo when its numerator and denominator are increased (decreased) by the same number?
372. $\frac{a+k}{b+k}-\frac{a}{b}=\frac{(b-a) k}{b(b+k)}$. Therefore, if the fraction was proper $(a<b)$, it approaches 1 from below, i.e., it is increasing; if improper $(a>b)$, it approaches 1 from above, i.e., it is decreasing.