If 3xC2=15, find the value of x?
2
4
5
6
Correct answer is A
3xC2=3x(3x−1)(3x−2)!(3x−2)!2!=15
3x(3x−1)=30⟹9x2−3x−30=0
9x2−18x+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 = 16+172=332=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−ˉx | -1 | 2 | -2 | -3 | 3 | 1 | |
| (x−ˉx)2 | 1 | 4 | 4 | 9 | 9 | 1 | 28 |
ˉx=246=4
S.D=√∑(x−ˉx)2n
= √286=√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
= 8C3=8!(8−3)!3!
= 8×7×63×2
= 56 ways
154
1354
2027
4154
Correct answer is B
P(only one hit target) = P(Kofi not Ama) + P(Ama not Kofi)
P(Kofi not Ama) = P(Kofi and Ama') = 16×89=854
P(Ama not Kofi) = P(Ama and Kofi') = 19×56=554
P(only one hit target) = 854+554=1354