Final answer:
Peak height velocity in girls occurs at about age 11.5 years, while it occurs at about age 13.5 in boys. Growth in height is completed by about 16 years in girls and by about age 18 in boys.
Step-by-step explanation:
Peak height velocity in girls occurs at about age 11.5 years when growth in height is about 9 cm (3.5 in.) per year on average. Growth in height in girls is completed by about 16 years when the closure of the epiphyses prevents any additional growth in height.
In boys, peak height velocity occurs at about age 13.5 when growth in height is about 10.3 cm (4 in.) per year on average. Growth in height in boys ceases by about age 18 when the ends of the long bones finally ossify at the epiphyses, so additional growth in height is no longer possible.