Question

A doctor uses the formula in the box to calculate patients'body mass index (BMI).A patient is described as underweight if their BMI is below 18.5 .
a Tina's mass is 48.8$kg$ and her height is 1.56$m.$ Is she underweight? Explain your answer.
b Stephen's height is 1.80$m$ and his mass is 68.5$kg$ . He wants to have a BMI of $20.$How many kilograms must he lose to reach a BMI of 20 ? Show your working.

Formula used by doctor for BMI: $=\frac{m}{h^2}$ where: $m$ is the mass in kilograms and $h$ is the height in metres.

Answer 1

a. Tina $=\frac{18.8kg}{\left(1.56m\right)}$

=20.05 BMI

Tina is not underweight because her

BMI $>$ 18.5.

b. Present BMI of stephen

$=\frac{68.5}{(1.80{)}^2}=21.14$

$\Rightarrow \frac{68.5-x}{(1.90{)}^2}=20$

$\Rightarrow x=3.7$