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- Question
- A and B start from the same point and travel in the same direction round a circular track 3 km in circumference. If their speed be 200 and 150 metres a minute, when will they first together again at the starting point?
Options- A. 40 min
- B. 55 min
- C. 1 hour
- D. 45 min
- Correct Answer
- 1 hour
ExplanationTime taken by A in one round = 3000 / 200 = 15 min.
Time taken by B in one round = 3000 / 150 = 20 min
L.C.M. of 15 min and 20 min = 60 min = 1 hr.
Hence, they will meet first together at the starting point after 1 hour.
2nd Method to solve this
Let us assume after T minutes both A and B will meet first time together at starting points.
According to question,
Distance covered by A in T minutes = 200 x T = 200T
Distance covered by B in T minutes = 150 x T = 150T
200T - 150T = 3000 As we know (3 KM = 3000 meters)
? 50T = 3000
? 5T = 300
? T = 300/5 = 60 Minutes.
As we know ( 60 minutes = 1 hours)
? T = 1 Hours - 1. Five bells begin to toll together and toll respectively at intervals of 6, 7, 8, 9 and 12 seconds. How many times they will toll together in one hour , excluding the one at the start?
Options- A. 3
- B. 5
- C. 7
- D. 9 Discuss
- 2. The average score of a cricketer for 10 matches is 43.9 runs. If the average for the first six matches is 53 , the average for the last four matches is?
Options- A. 17.15
- B. 29.75
- C. 30.25
- D. 31 Discuss
- 3. Twelve men can complete a work in 8 days. Three days after they started the work, 3 more men joined them. In how, many days will all of them together complete the remaining work
Options- A. 2
- B. 4
- C. 5
- D. 6 Discuss
- 4. 3 yr before, the average age of a family of 5 members was 17 yr. Due to birth of a new child, the average age is same today. The present age of child is?
Options- A. 1 yr
- B. 3 yr
- C. 21/2 yr
- D. 2 yr Discuss
- 5. A number when divided by 5, leaves 3 as a remainder. What will be the remainder when the square of this number is divided by 5.
Options- A. 3
- B. 4
- C. 5
- D. 0 Discuss
- 6. The ratio between the present ages of Tarun and Varun is 3 : 7, respectively. After 4 yr, Varun's age will be 39 yr. What was Tarun's age 4 yr ago?
Options- A. 12 yr
- B. 13 yr
- C. 19 yr
- D. 18 yr Discuss
- 7. The ages of Harsh and Sumit are 40 yr and 60 yr, respectively. How many year before the ratio of their ages was 3 : 5?
Options- A. 15 yr
- B. 20 yr
- C. 37 yr
- D. 10 yr Discuss
- 8. The mean marks of 30 students in a class is 58.5. Later on, it was found that 75 was wrongly recorded as 57. Find the correct mean.
Options- A. 57.4
- B. 57.5
- C. 58.9
- D. 59.1 Discuss
- 9. A library has 'a' copies of one book, 'b' copies of each of two book, 'c' copies of each of three books and single copy of 'd' book. The number of ways in which these books can be distribute is?
Options- A. (a + b + c + d)! / (a! b! c!)
- B. (a + 2b + 3c + d)! / {a! (b!)2 (c!)3}
- C. (a + 2b + 3c + d )! / (a! b! c!)
- D. None of these Discuss
- 10. If three marbles are picked at random, what is the probability that either all are green or all are red?
Options- A. 7/44
- B. 7/12
- C. 5/12
- D. 1/44 Discuss
More questions
Correct Answer: 7
Explanation:
L.C.M of 6, 7, 8, 9, 12 is 504
So, the bells will toll together after 504 sec.
In hour, they will toll together
= (60 x 60) / 504 times
= 7 times
Correct Answer: 30.25
Explanation:
Let the average for last 4 matches be y.
Sum of score for 10 matches = sum of score for first 6 matches + sum of score of last 4 matches.
So 53 x 6 + 4y = 10 x 43.9
? 4x= 439-318
?4x= 121
? x= 30.25
Correct Answer: 4
Explanation:
1 men's one day's work = 1/96
12 men's 3 day's work = 3 x (1/8) = 3/8
Remaining work = (1 - 3/8) = 5/8
15 men's 1 day's work = 15/96
Now, 15/96 work is done by them in 1 day
? 5/8 work will be done by them in = (96/15) x (5/ 8) i.e., 4 days
Correct Answer: 2 yr
Explanation:
3 yr before, total age of 5 members = 17 x 5 = 85 yr
? The present age of all members of family = 85 + 3 x 5 = 100 yr
Let the age of child be N yr.
? Present average age of family including the child
= (100 + N)/6
? 17 = (100 + N)/6
? N = 102 - 100 = 2 yr
Correct Answer: 4
Explanation:
Let the number be N.
Therefore N = 5k + 3
On squaring both sides, we get
N2 = ( 5k + 3)2
= 5( 5k2 + 6k +1 ) + 4
? On dividing x2 by 5, the remainder is 4
Correct Answer: 18 yr
Explanation:
Let Tarun and Varun's ages are 3k yr and 7k yr, respectively.
? 7k + 4 = 39
? k = 5
Hence, Tarun's age 4 yr ago = 3 x 5 - 4 = 11 yr
Correct Answer: 10 yr
Explanation:
Let k yr before, the ratio of their ages was 3 : 5.
According to the question
(40 - k)/(60 - k) = 3/5
? 200 - 5k = 180 - 3k
? 2k = 20
? k = 10
Correct Answer: 59.1
Explanation:
Correct mean = ( sum of total marks - 57 + 75 ) / 30
= ( 30 x 58.5 - 57 + 75 ) / 30
= (1755 + 18 ) / 30
= 59.1
Correct Answer: (a + 2b + 3c + d)! / {a! (b!)2 (c!)3}
Explanation:
Total number of books = a + 2b + 3c + d . Since there are 'b' copies of each of two books, 'c' copies of each of three books and single copy of 'd' book.
Therefore, the total number of arrangements is = (a + 2b + 3c + d )! / {a! (b!)2 (c!)3}
Correct Answer: 1/44
Explanation:
Total number of ways of selection of 3 marbles out of 12
= n(S) = 12C3 = 220
Total number of favorable events = n(E)
= 3C3 + 4C3 = 1 + 4 = 5
? Required probability
= 5/220 = 1/44
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