4.1.1 Explain what it means if the baby's weight-for-age relationship is on the 85th percentile curve - NSC Mathematical Literacy - Question 4 - 2016 - Paper 1

An 11-month-old baby on the 50th percentile for weight typically weighs around 9.4 kg. This represents the median weight, meaning half of the babies weigh less than this and half weigh more.

To determine the percentile curve for the 18-month-old baby weighing 11 kg, a comparison with the growth chart is needed. Generally, a weight of 11 kg for an 18-month-old is around the 75th percentile, indicating that the baby weighs more than about 75% of his peers.

The BMI is calculated using the formula:

$BMI = \frac{Weight (in kg)}{(Height in metres)^2}$

1. Convert height to metres: 80 cm = 0.8 m.
2. Substitute values into the formula:

$BMI = \frac{11 \text{ kg}}{(0.8 \text{ m})^2}$

3. Calculate:

$BMI = \frac{11}{0.64} = 17.19 \text{ kg/m}^2$

Thus, the BMI for this baby is approximately 17.19 kg/m².