A-Level Edexcel Biology Changing the Subject of an Equation

Review A-Level Edexcel Biology changing the subject of an equation through BMI calculation evidence, including rearrangement, substitution and rounding.

Exam points

rearrange BMI equations, substitute table values and round calculated mass correctly

[Maximum number: 3]

Obesity increases the risk of cardiovascular disease (CVD).
Body mass index (BMI), waist-to-hip ratio (WHR) and skinfold thickness are indicators of obesity.

The table shows some measurements taken from two females, female J and female K.

Table for Question A.2.2—Changing the subject of an equation question 1 — Edexcel A-Level Biology AS

The formula for calculating BMI is:

\mathrm{BMI}=\frac{\text { mass in } \mathrm{kg}}{(\text { height in } \mathrm{m})^{2}}

Calculate the mass of female K, using the data in the table.

An answer that includes the following points:

- height ${ }^{2}$ calculated ( 1 )

- equation rearranged and values substituted in (1)

- answer given to $\{1$ decimal place / 3 significant figures $\}$ (1)

$2.4025\left(\mathrm{~m}^{2}\right) / 24025\left(\mathrm{~cm}^{2}\right)$ $\text { mass }=36 \times 2.4025 / 86.49$

86.5

NB CE if rounded $\mathrm{cm}^{2}$ value to 865 000

Correct answer of 86.5 with no working shown should be awarded 3 marks.

An answer of 86.49 or 865000 with no working shown should be awarded 2 marks.

(3)

All question bank results loaded

A.2.2—Changing the subject of an equation question 1