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Date November 2021 Marks available 3 Reference code 21N.1.SL.TZ0.6
Level Standard Level Paper Paper 1 Time zone Time zone 0
Command term Estimate Question number 6 Adapted from N/A

Question

Inspectors are investigating the carbon dioxide emissions of a power plant. Let R be the rate, in tonnes per hour, at which carbon dioxide is being emitted and t be the time in hours since the inspection began.

When R is plotted against t, the total amount of carbon dioxide produced is represented by the area between the graph and the horizontal t-axis.

The rate, R, is measured over the course of two hours. The results are shown in the following table.

 

Use the trapezoidal rule with an interval width of 0.4 to estimate the total amount of carbon dioxide emitted during these two hours.

[3]
a.

The real amount of carbon dioxide emitted during these two hours was 72 tonnes.

Find the percentage error of the estimate found in part (a).

[2]
b.

Markscheme

attempt at using trapezoidal rule formula              (M1)

122-0530+50+250+60+40+20            (A1)

(total carbon =) 84  tonnes            A1

 

[3 marks]

a.

84-7272×100%              (M1)


Note: Award (M1) for correct substitution of final answer in part (a) into percentage error formula.


=16.7%  16.6666%            A1

 

[2 marks]

b.

Examiners report

Although there were successful attempts at using the trapezoidal rule formula, there was quite a bit of confusion among candidates as to which values were to be substituted. It seemed that a significant number of candidates were approaching it with some confusion due to a lack of practice of using the trapezoidal rule formula. Calculation of percentage error in part (b) was generally well done by most candidates.

a.

Although there were successful attempts at using the trapezoidal rule formula, there was quite a bit of confusion among candidates as to which values were to be substituted. It seemed that a significant number of candidates were approaching it with some confusion due to a lack of practice of using the trapezoidal rule formula. Calculation of percentage error in part (b) was generally well done by most candidates.

b.

Syllabus sections

Topic 1—Number and algebra » SL 1.6—Approximating and estimating
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