A 9‑year‑old girl’s height increases by 5 cm in 4 months during early puberty. If she maintains this average rate, how many months will it take her to gain an additional 15 cm?

Step-by-step solution

1. Calculate the average monthly growth: $\frac{5\text{ cm}}{4\text{ months}}=1.25\text{ cm/month}$.
2. Determine the number of months required for a 15 cm gain: $\frac{15\text{ cm}}{1.25\text{ cm/month}}=12\text{ months}$.
3. Conclude that it will take 12 months for the girl to gain 15 cm at this rate.

Concept tested: Projection of growth during puberty

Published 7 October 2026 · How this solution was prepared and checked