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- Question
A problem is given to three students whose chances of solving it are 1/2, 1/3 and 1/4 respectively. What is the probability that the problem will be solved?
Options- A. 1/4
- B. 1/2
- C. 3/4
- D. 7/12
- Correct Answer
- 3/4
ExplanationLet A, B, C be the respective events of solving the problem and be the respective events of not solving the problem. Then A, B, C are independent event
are independent events
Now, P(A) = 1/2 , P(B) = 1/3 and P(C)=1/4
P( none solves the problem) = P(not A) and (not B) and (not C)
=
=
=
=
Hence, P(the problem will be solved) = 1 - P(none solves the problem)
= = 3/4
- 1. A certain distance is covered at a certain speed. If half of this distance is covered in double the time, the ratio of the two speed is?
Options- A. 4:1
- B. 1.4
- C. 2:1
- D. 1:2 Discuss
- 2. The length of the train that takes 8 second to pass a pole where it runs at a speed of 36 km/hr is?
Options- A. 288 meters
- B. 45 meters
- C. 48 meters
- D. 80 meters Discuss
- 3. Two goods train each 500 m long, are running in opposite directions on parallel tracks. Their speeds are 45 km/hr and 30 km/hr respectively. Find the time taken by the slower train to pass the driver of the faster one.
Options- A. 12 sec
- B. 24 sec
- C. 48 sec
- D. 60 sec Discuss
- 4. A jogger running at 9 kmph alongside a railway track in 240 metres ahead of the engine of a 120 metres long train running at 45 kmph in the same direction. In how much time will the train pass the jogger?
Options- A. 3.6 sec
- B. 18 sec
- C. 36 sec
- D. 72 sec Discuss
- 5. A train 108 m long moving at a speed of 50 km/hr crosses a train 112 m long coming from opposite direction in 6 seconds. The speed of the second train is:
Options- A. 48 km/hr
- B. 54 km/hr
- C. 66 km/hr
- D. 82 km/hr Discuss
- 6. Two stations A and B are 110 km apart on a straight line. One train starts from A at 7 a.m. and travels towards B at 20 kmph. Another train starts from B at 8 a.m. and travels towards A at a speed of 25 kmph. At what time will they meet?
Options- A. 9 a.m.
- B. 10 a.m.
- C. 10.30 a.m.
- D. 11 a.m. Discuss
- 7. Two goods train each 500 m long, are running in opposite directions on parallel tracks. Their speeds are 45 km/hr and 30 km/hr respectively. Find the time taken by the slower train to pass the driver of the faster one.
Options- A. 12 sec
- B. 24 sec
- C. 48 sec
- D. 60 sec Discuss
- 8. When a plot is sold for Rs. 18,700, the owner loses 15%. At what price must that plot be sold in order to gain 15%?
Options- A. Rs. 21,000
- B. Rs. 22,500
- C. Rs. 25,300
- D. Rs. 25,800 Discuss
- 9. If x and y are the two digits of the number 653xy such that this number is divisible by 80, then x + y =?
Options- A. 2 or 6
- B. 4
- C. 4 or 8
- D. 8
- E. None of these Discuss
- 10. The difference of the squares of two consecutive odd integers is divisible by which of the following integers?
Options- A. 3
- B. 6
- C. 7
- D. 8 Discuss
More questions
Correct Answer: 4:1
Explanation:
Let x km . be covered in y hrs.
then, 1st speed = (x / y) km/hr.
2nd speed = [(x/2) / 2y)] km/hr.
= (x/4y) km/hr.
? Ratio of speed = x/y : x/4y = 1 :1/4 = 4: 1
Correct Answer: 80 meters
Explanation:
Speed of the train = (36 x 5)/18 = 10 m/sec.
Distance = (Time x Speed ) = (8 x 10 ) = 80 meters
? Length of the train = 80 meters
Correct Answer: 24 sec
Explanation:
| Relative speed = | = (45 + 30) km/hr | |||||||
|
||||||||
|
We have to find the time taken by the slower train to pass the DRIVER of the faster train and not the complete train.
So, distance covered = Length of the slower train.
Therefore, Distance covered = 500 m.
| ∴ Required time = | ❨ | 500 x | 6 | ❩ | = 24 sec. |
| 125 |
Correct Answer: 36 sec
Explanation:
Speed of train relative to jogger = (45 - 9) km/hr = 36 km/hr.
| = | ❨ | 36 x | 5 | ❩m/sec |
| 18 |
= 10 m/sec.
Distance to be covered = (240 + 120) m = 360 m.
Correct Answer: 82 km/hr
Explanation:
Let the speed of the second train be x km/hr.
| Relative speed | = (x + 50) km/hr | |||||||
|
||||||||
|
Distance covered = (108 + 112) = 220 m.
| ∴ | 220 | = 6 | ||
|
⟹ 250 + 5x = 660
⟹ x = 82 km/hr.
Correct Answer: 10 a.m.
Explanation:
Suppose they meet x hours after 7 a.m.
Distance covered by A in x hours = 20x km.
Distance covered by B in (x - 1) hours = 25(x - 1) km.
∴ 20x + 25(x - 1) = 110
⟹ 45x = 135
⟹ x = 3.
So, they meet at 10 a.m.
Correct Answer: 24 sec
Explanation:
| Relative speed = | = (45 + 30) km/hr | |||||||
|
||||||||
|
We have to find the time taken by the slower train to pass the DRIVER of the faster train and not the complete train.
So, distance covered = Length of the slower train.
Therefore, Distance covered = 500 m.
| ∴ Required time = | ❨ | 500 x | 6 | ❩ | = 24 sec. |
| 125 |
Correct Answer: Rs. 25,300
Explanation:
85 : 18700 = 115 : x
| ⟹ x = | ❨ | 18700 x 115 | ❩ | = 25300. |
| 85 |
Hence, S.P. = Rs. 25,300.
Correct Answer: 2 or 6
Explanation:
80 = 2 x 5 x 8
Since 653xy is divisible by 2 and 5 both, so y = 0.
Now, 653x is divisible by 8, so 13x should be divisible by 8.
This happens when x = 6.
∴x + y = (6 + 0) = 6.
Correct Answer: 8
Explanation:
Let the two consecutive odd integers be (2 n + 1) and (2 n + 3). Then,
(2n + 3)2 - (2n + 1)2 = (2n + 3 + 2n + 1) (2n + 3 - 2n - 1)
= (4n + 4) x 2
= 8(n + 1), which is divisible by 8.
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