Edexcel IGCSE Biology Arithmetic Mean

Practise Edexcel IGCSE Biology arithmetic mean calculations by averaging repeated volumes, masses and daily production data in context.

[Maximum number: 3]

Pineapple juice contains a protease called bromelain.
A student uses this method to investigate the digestion of solid gelatine protein by bromelain.
- place solid gelatine protein into a test tube up to a height of 5 cm
- mix $5 \mathrm{~cm}^{3}$ pineapple juice with $1 \mathrm{~cm}^{3}$ of pH 4 buffer
- place $1 \mathrm{~cm}^{3}$ of the pineapple juice and buffer solution on top of the gelatine
- leave for one hour in a water bath set to $37^{\circ} \mathrm{C}$
- measure the height of the solid gelatine and use it to calculate the volume of gelatine that has been digested

Repeat the method three more times.
The diagram shows part of the student's method.

Figure for Question 2B Arithmetic mean question 1 — Edexcel IGCSE Biology

The table shows the student's results for the volumes of gelatine digested at pH 4 .

Table for Question 2B Arithmetic mean question 1 — Edexcel IGCSE Biology

Calculate the mean volume of gelatine digested in $\mathrm{cm}^{3}$ .

Give your answer to two decimal places.

0.57

0.57 gains all three marks

Accept 0.90 for two marks

OR

Accept 0.56 or $0.56(66666 \ldots .7)$ or 0.56

recurring for two marks

Accept 0.9 or 0.8975 or 1.7 or $\div 3$
for one mark

Example calculation (not mark points):

(0.55+0.54+0.61)=1.7 $\div 3$

to two dp

Correct answer with no working gains all three
marks.

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2B Arithmetic mean question 1