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- Question
A box contains 2 white balls, 3 black balls and 4 red balls. In how many ways can 3 balls be drawn from the box, if at least one black ball is to be included in the draw?
Options- A. 32
- B. 48
- C. 64
- D. 96
- E. None of these
- Correct Answer
- 64
ExplanationWe may have(1 black and 2 non-black) or (2 black and 1 non-black) or (3 black).∴ Required number of ways = (3C1 x 6C2) + (3C2 x 6C1) + (3C3) = ❨ 3 x 6 x 5 ❩ + ❨ 3 x 2 x 6 ❩ + 1 2 x 1 2 x 1 = (45 + 18 + 1) = 64.
More questions
- 1. Shankara buys a watch for Rs. 1,950 in cash and sells it for Rs. 2,200 at a credit of 1 year. If the rate of interest is 10% per annum, he _____ :
Options- A. gains Rs. 55
- B. gains Rs. 50
- C. loses Rs. 30
- D. gains Rs. 30 Discuss
Correct Answer: gains Rs. 50
Explanation:
- 2. ABCD is a rhombus with ? ABC = 56°, then ? ACD is equal to :
Options- A. 90°
- B. 60°
- C. 56°
- D. 62° Discuss
Correct Answer: 62°
Explanation:
- 3. The shaded region represents
Options- A. y ? x
- B. y ? ? x
- C. y ? x
- D. y ? ? x Discuss
Correct Answer: y ? x
Explanation:
The shaded region represents
y ? x- 4. 45 x? = 25% of 900
Options- A. 16.20
- B. 4
- C. 5
- D. 500 Discuss
Correct Answer: 5
Explanation:
Let 45 x A = (25 x 900)/100
? A = (25 x 9)/45 = 5- 5. Rajan sold an articles for ? 6000 at a loss of 25%. Find the cost price.?
Options- A. ? 7500
- B. ? 7200
- C. ? 8000
- D. ? 8500 Discuss
Correct Answer: ? 8000
Explanation:
CP = [100/(100 - Loss%) ] x SP
CP = 6000 x (100/75) = 8000- 6. In which of the following cases, A = B?
Options- A. A = {12, 14, 16}, B = {16, 18, 20}
- B. A = ?, b = {}
- C. A = {x: x ? W and x < 1}, B = ?
- D. A = {x: x is a day of the week beginning with S}, B = {Sunday} Discuss
Correct Answer: A = ?, b = {}
Explanation:
NA
- 7. 10, 25, 45, 54, 60, 75, 80
Options- A. 10
- B. 45
- C. 54
- D. 75 Discuss
Correct Answer: 54
Explanation:
Each of the numbers except 54 is multiple of 5.- 8. If two parallel lines are intersected by a transversal, then the bisectors of the two pairs of interior angles enclose a:
Options- A. Trapezium
- B. Rectangle
- C. Square
- D. circle Discuss
Correct Answer: Rectangle
Explanation:
- 9. ?. 6x 2 + 77x + 121 = 0
?. y 2 + 9y ? 22 = 0
Options- A. 1
- B. 2
- C. 3
- D. 4 Discuss
Correct Answer:
Explanation:
- 10. The length of minute hand of a wall clock is 7 cms. The area swept by minute hand in 30 minutes is?
Options- A. 147 sq. cm
- B. 210 sq. cm
- C. 154 sq. cm
- D. 77 sq. cm Discuss
Correct Answer: 77 sq. cm
Explanation:
Angle swept in 30 min= 180°
Area swept = [(22/7) x 7 x 7] x [180°/360°] cm2
= 77 cm2
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