Directions(1–3): What value should come in the place of (?) in the following number series?
1. 4080, 3360, 2730, 2184, 1716, ?
A. 1320
B. 1850
C. 1560
D. 1210
E. 1080
2. 3, 21, 33, 39, 39, ?
A. 52
B. 48
C. 33
D. 28
E. 22
3. 19, 17, 30, 82, 312, ?
A. 1528
B. 1236
C. 1328
D. 1124
E. 1456
4. Three unbiased coins are tossed. What is the probability of getting at least 2 tails?
A. 0.75
B. 0.5
C. 0.25
D. 0.2
E. None of these
5. Tickets numbered 1 to 50 are mixed and one ticket is drawn at random. Find the probability that the ticket drawn has a number which is a multiple of 4 or 7?
A. [latex]\frac {9}{25}[/latex]
B. [latex]\frac {9}{50}[/latex]
C. [latex]\frac {18}{25}[/latex]
D. [latex]\frac {1}{25}[/latex]
E. None of these
Answers and Explanations
1. Answer - Option A
Explanation -
[latex]{16}^{3}[/latex] – 16 = 4080
[latex]{15}^{3}[/latex] – 15 = 3360
[latex]{14}^{3}[/latex] – 14 = 2730
[latex]{13}^{3}[/latex] – 13 = 2184
[latex]{12}^{3}[/latex] – 12 = 1716
[latex]{11}^{3}[/latex] – 11 = 1320
2. Answer - Option C
Explanation -
3 + (3 * 6) = 21
21 + (2 * 6) = 33
33 + (1 * 6) = 39
39 + (0 * 6) = 39
39 + (-1 * 6) = 33
3. Answer - Option A
Explanation -
19 * 1 – 2 = 17
17 * 2 – 4 = 30
30 * 3 – 8 = 82
82 * 4 – 16 = 312
312 * 5 – 32 = 1528
4. Answer - Option B
Explanation -
S = {HHH, HHT, HTH, HTT, THH, THT, TTH, TTT}
E = {HTT, THT, TTH, TTT}
n(S) = 8
n(E) = 4
P(E) =[latex]\frac {n(E)}{ n(S)} = \frac {4}{8}[/latex] = 0.5
5. Answer - Option A
Explanation -
S = {1, 2, 3, … , 49, 50}
E = {4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 7, 14, 21, 35, 42, 49}
n(S) = 50
n(E) = 18
P(E) = [latex]\frac {n(E)}{ n(S)} = \frac {18}{50} = \frac {9}{25}[/latex]