Home / IBDP Maths SL 4.3 Measures of central tendency AA HL Paper 1- Exam Style Questions

IBDP Maths SL 4.3 Measures of central tendency AA HL Paper 1- Exam Style Questions

IBDP Maths SL 4.3 Measures of central tendency AA HL Paper 1- Exam Style Questions- New Syllabus

Question

Claire rolls a six-sided die 16 times. The scores obtained are shown in the following frequency table.

Frequency table of die rolls

It is given that the mean score is 3.

(a) Find the value of p and the value of q.

Each of Claire’s scores is multiplied by 10 to determine the final score for a game.

(b) Write down the mean final score.

▶️ Answer/Explanation
Solution (a)

Step 1: Total frequency equation

From the table, sum of all frequencies = 16:

\( p + q + 4 + 2 + 0 + 3 = 16 \)

\( p + q + 9 = 16 \)

\( p + q = 7 \)  (Equation 1)

Step 2: Mean score equation

Given mean = 3, so total sum = 16 × 3 = 48:

\( (1×p) + (2×q) + (3×4) + (4×2) + (5×0) + (6×3) = 48 \)

\( p + 2q + 12 + 8 + 0 + 18 = 48 \)

\( p + 2q = 10 \)  (Equation 2)

Step 3: Solve the system

Subtract Equation 1 from Equation 2:

\( (p + 2q) – (p + q) = 10 – 7 \)

\( q = 3 \)

Substitute back into Equation 1:

\( p + 3 = 7 \)

\( p = 4 \)

Final answers: \(\boxed{p = 4}\), \(\boxed{q = 3}\)

Solution (b)

Mean final score calculation:

When all scores are multiplied by 10, the mean is also multiplied by 10:

New mean = Original mean × 10 = 3 × 10 = \(\boxed{30}\)

Alternative calculation:

\( \frac{10(1×4) + 20(3) + 30(4) + 40(2) + 50(0) + 60(3)}{16} = \frac{480}{16} = 30 \)

Question

On a Monday at an amusement park, a sample of 40 visitors was randomly selected as they were leaving the park. They were asked how many times that day they had been on a ride called The Dragon. This information is summarized in the following frequency table.

Frequency table

It can be assumed that this sample is representative of all visitors to the park for the following day.

  1. For the following day, Tuesday, estimate
    1. the probability that a randomly selected visitor will ride The Dragon;
    2. the expected number of times a visitor will ride The Dragon.
  2. It is known that 1000 visitors will attend the amusement park on Tuesday. The Dragon can carry a maximum of 10 people each time it runs. Estimate the minimum number of times The Dragon must run to satisfy demand.
▶️ Answer/Explanation
Solution (a)(i)

To estimate the probability that a randomly selected visitor will ride The Dragon on Tuesday, we consider the frequency data provided from Monday’s sample. The total number of visitors sampled is 40. The number of visitors who rode The Dragon at least once is:

\[ 16 \text{ (once)} + 13 \text{ (twice)} + 2 \text{ (three times)} + 3 \text{ (four times)} = 34 \]

The probability is therefore:

\[ \frac{34}{40} = \frac{17}{20} = 0.85 \]

\(\boxed{0.85}\)

Solution (a)(ii)

The expected number of times a visitor will ride The Dragon is calculated using the expected value formula:

\[ E(X) = \sum [x \times P(X = x)] \]

Calculating each term:

\[ (0 \times \frac{6}{40}) + (1 \times \frac{16}{40}) + (2 \times \frac{13}{40}) + (3 \times \frac{2}{40}) + (4 \times \frac{3}{40}) \]

\[ = 0 + \frac{16}{40} + \frac{26}{40} + \frac{6}{40} + \frac{12}{40} = \frac{60}{40} = 1.5 \]

\(\boxed{1.5 \text{ times}}\)

Solution (b)

First calculate the total expected rides for 1000 visitors:

\[ 1.5 \text{ rides/visitor} \times 1000 \text{ visitors} = 1500 \text{ rides} \]

With a capacity of 10 people per run:

\[ \frac{1500 \text{ rides}}{10 \text{ people/run}} = 150 \text{ runs} \]

\(\boxed{150 \text{ runs}}\)

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