The table shows the mark obtained by students in a test. Marks 1 2 3
FURTHER MATHEMATICS
WAEC 2023
The table shows the mark obtained by students in a test.
| Marks | 1 | 2 | 3 | 4 | 5 |
| Frequency | 2 | k | 1 | 1 | 2 |
If the mean mark is 3, find the value of k.
- A. 4
- B. 1
- C. 2
- D. 3
Correct Answer: B. 1
Explanation
x? \(=\frac{∑fx}{∑f}= 3\)
\(=\frac{(1 \times 2)+(2 \times k)+(3 \times 1)+(4 \times 1)+(5 \times 2)}{2 + k + 1 + 1 + 2}= 3\)
\(=\frac{2 + 2k + 3 + 4 + 10}{6 + k} = 3\)
\(=\frac{19 + 2k}{6 + k} = 3\)
\(=\frac{19 + 2k}{6 + k} = \frac{3}{1}\)
=19+2k=3(6+k)
=19+2k=18+3k
=2k-3k=18-19
=-k=-1
∴k=1
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