Final answer:
Alexandra is incorrect; her sister grew 2 1/2 inches, not 38 3/4 inches over the last year. The announced growth would be physically implausible for a one-year period.
Step-by-step explanation:
The question is about calculating the growth in height of a girl from one birthday to the next. Alexandra initially measured her sister as being 36 1/4 inches tall and on the next birthday as 38 3/4 inches tall. To determine if the sister grew 38 3/4 inches over the last year, we need to calculate the difference between the two measurements:
38 3/4 inches (current height) - 36 1/4 inches (previous height) = 2 1/2 inches.
Therefore, Alexandra's sister grew 2 1/2 inches, not 38 3/4 inches as Alexandra announced. It does not make sense to say that her sister grew 38 3/4 inches because this would mean her sister's height would have more than doubled in just one year, which is not physically plausible for a growing child. The correct amount of growth is 2 1/2 inches.