Directions(1-5): Probability
1. A bag contains 6 black and 8 white balls. One ball is drawn at random. What is the probability that the ball drawn is white?
A. [latex]\frac{3}{4}[/latex]
B. [latex]\frac{4}{7}[/latex]
C. [latex]\frac{1}{8}[/latex]
D. [latex]\frac{3}{7}[/latex]
Answer : Option B
Explanation: Let number of balls = (6 + 8) = 14.
A number of white balls = 8.
P (drawing a white ball) = [latex]\frac{8}{14}[/latex]
= [latex]\frac{4}{7}[/latex]
2. One card is drawn at random from a pack of 52 cards. What is the probability that the card drawn is a face card (Jack, Queen and King only)?
A. [latex]\frac{1}{13}[/latex]
B. [latex]\frac{3}{13}[/latex]
C. [latex]\frac{1}{4}[/latex]
D. [latex]\frac{9}{52}[/latex]
Answer : Option B
Explanation: Clearly, there are 52 cards, out of which there are 12 face cards.
P (getting a face card) = [latex]\frac{12}{52}[/latex]
∴ = [latex]\frac{3}{13}[/latex]
Directions(1-5): Mensuration
3. A circular wire of radius 42 cm is cut and bent in the form of a rectangle whose sides are in the ratio of 6:5. The smaller side of the rectangle is :
A. 30 cm
B. 60 cm
C. 72 cm
D. 132 cm
Answer : Option B
Explanation: circumference = [latex]\frac{2*22}{7*42}[/latex] = 264 cm
length of rectangle sides are 6x, 5x. then circumference is 2*(6x+5x) = 264, x = 12
smaller side of rectangle = 5x = 60 cm
4. The length of a rectangle is twice its breadth. If its length is decreased by 5 cm and the breadth is increased by 5 cm, the area of the rectangle is increased by 75 cm2. Therefore, the length of the rectangle is :
A. 20 cm
B. 30 cm
C. 40 cm
D. 50 cm
Answer : Option C
Explanation: b=x and l= 2x
then (2x-5)(x+)-x*2x= 75
2[latex]{x}^{2}[/latex] + 5x-25-2[latex]{x}^{2}[/latex] = 75
x = 20
length = 40 cm
Directions(1-5): Averages
5. The average weight of A, B and C is 45 kg. If the average weight of A and B be 40 kg and that of B and C be 43 kg, then the weight of B is:
A. 17 kg
B. 20 kg
C. 26 kg
D. 31 kg
Answer : Option D
Explanation: Let A, B, C represent their respective weights. Then, we have:
A + B + C = (45 x 3) = 135 .... (i)
A + B = (40 x 2) = 80 .... (ii)
B + C = (43 x 2) = 86 ....(iii)
Adding (ii) and (iii), we get: A + 2B + C = 166 .... (iv)
Subtracting (i) from (iv), we get : B = 31.
B's weight = 31 kg.