48
60
240
720
Correct answer is A
No explanation has been provided for this answer.
If \(^{3x}C_{2} = 15\), find the value of x?
2
4
5
6
Correct answer is A
\(^{3x}C_{2} = \frac{3x(3x - 1)(3x - 2)!}{(3x - 2)! 2!} = 15\)
\(3x(3x - 1) = 30 \implies 9x^{2} - 3x - 30 = 0\)
\(9x^{2} - 18x + 15x - 30 = 9x(x - 2) + 15(x - 2) = 0\)
\((9x + 15)(x - 2) = 0\)
x = 2.
| Marks | 5-7 | 8-10 | 11-13 | 14-16 | 17-19 | 20-22 |
| No of students | 4 | 7 | 26 | 41 | 14 | 8 |
The table above shows the distribution of marks of students in a class. Find the upper class boundary of the modal class.
13.5
16
16.5
22.5
Correct answer is C
The modal class = 14 - 16
The upper class boundary = \(\frac{16 + 17}{2} = \frac{33}{2} = 16.5\)
Find the standard deviation of the numbers 3,6,2,1,7 and 5.
2.00
2.16
2.50
2.56
Correct answer is B
| \(x\) | 3 | 6 | 2 | 1 | 7 | 5 | Total = 24 |
| \(x - \bar{x}\) | -1 | 2 | -2 | -3 | 3 | 1 | |
| \((x - \bar{x})^{2}\) | 1 | 4 | 4 | 9 | 9 | 1 | 28 |
\(\bar{x} = \frac{24}{6} = 4\)
\(S.D = \sqrt{\frac{\sum (x - \bar{x})^{2}}{n}}\)
= \(\sqrt{\frac{28}{6}} = \sqrt{4.667} = 2.16\)
In how many ways can 3 prefects be chosen out of 8 prefects?
6
24
56
336
Correct answer is C
= \(^{8}C_{3} = \frac{8!}{(8 - 3)! 3!}\)
= \(\frac{8 \times 7 \times 6}{3 \times 2}\)
= 56 ways