Directions(1 – 3): What value should come in the place of question mark (?) in the following questions?
1. [latex]\sqrt{6084}[/latex] ÷ 3 + 45 = ? – 12376 ÷ 7
A. 1839
B. 1945
C. 1757
D. 1653
E. None of these
2. [latex](\frac {5}{11}) of 5038 + 56 % of 1250 = {(?)}^{2} – 35[/latex]
A. 45
B. 30
C. 75
D. 55
E. None of these
3. [latex]{6}^{?} \times \sqrt{484} = 48090 ÷ 7 + 21642[/latex]
A. 7
B. 4
C. 9
D. 5
E. None of these
4. In a running race competition involving some boys and girls of an apartment, every member had to play exactly one race with every other member. It was found that in 10 races both the players were boys and in 45 races both the members were girls. Find the number of races in which one member was a boy and other was a girl.
A. 50
B. 40
C. 30
D. 20
E. None of these
5. A box consists of 15 balls numbered from 0 to 14. A boy picked a ball from the box and kept it in the bag after noting its number. He repeated this process 2 more times. What is the probability that the ball picked first by the boy is numbered higher than the ball picked second and the ball picked second by the boy is numbered higher than the ball picked third?
A. [latex]\frac{51}{3375}[/latex]
B. [latex]\frac{67}{3375}[/latex]
C. [latex]\frac{2197}{3375}[/latex]
D. [latex]\frac{329}{3375}[/latex]
E. None of these
Answers and Explanations
1. Answer - Option A
Explanation -
[latex](\frac {78}{3}) + 45 = x – (\frac {12376}{7})[/latex]
26 + 45 = x – 1768
X = 26 + 45 + 1768
X = 1839
2. Answer - Option D
Explanation -
[latex] (\frac{5}{11}) \times 5038 + (\frac {56}{100}) \times 1250 = {(x)}^{2} – 35[/latex]
[latex]2290 + 700 + 35 = {(x)}^{2}[/latex]
[latex]3025 = {(x)}^{2}[/latex]
X = 55
3. Answer - Option B
Explanation -
[latex]{6}^{?} \times 22 = (\frac {48090}{7}) + 21642[/latex]
[latex]{6}^{?} \times 22 = 6870 + 21642[/latex]
[latex]{6}^{?} = \frac {28512}{22}[/latex]
[latex]{6}^{?} = 1296[/latex]
[latex]{6}^{?} = {6}^{4}[/latex]
X = 4
4. Answer - Option A
Explanation -
Let the number of boys be x and girls be y.
No. of races played between boys = [latex]^{x}{C}_{2}[/latex] = 10 = x(x – 1) = 20 [latex]\Rightarrow[/latex] x = 5
Total number of boys participating in running race is 5.
No. of races played between girls = [latex]^{y}{C}_{2}[/latex] = 45 = y(y – 1) = 90 [latex]\Rightarrow[/latex] y = 10
Total number of girls participating in running race is 10.
Therefore, no of running races in which one player is boy and one is girl is,
= [latex] ^{5}{C}_{1} × ^{10}{C}_{1} = 5 \times 10 = 50[/latex]
5. Answer - Option C
Explanation -
Let the number on the ball picked first = a, second = b, third = c.
The order of a, b and c can be (a > b > c)
Number of ways selecting the first number = 13 (Because we can’t select 0 and 1)
Number of ways selecting the second number = 13 (Because we can’t select 0)
Number of ways selecting the third number = 13 (Because we can’t select first and third number)
Required probability = [latex]\frac {(13 \times 13 \times 13)}{153}[/latex]
= [latex]\frac {2197}{3375}[/latex]