How many way can we distribute 9 balls numbered from 1 to 9 in 9 boxes numbered from 1 to 9 such that each box contain exactly one ball and either of the balls with number 1 2 3 are not in boxes 1 2 3. Please help me solve the problem by not using n(AUBUC). Probably by using dearrangments.

Manu Jindal

3 years, 5 months ago

Hi Jayavignesh,

The solution to this question is as follows:

Total number of ways of distributing 9 balls = 9!.

Number of ways in which ball 1 is placed in box 1 = 8!

Number of ways in which ball 2 is placed in box 2 = 8!

Number of ways in which ball 3 is placed in box 3 = 8!

Number of ways in which balls 1 and 2 are placed in box 1 and 2 = 7!

Number of ways in which balls 2 and 3 are placed in box 2 and 3 = 7!

Number of ways in which balls 1 and 3 are placed in box 1 and 3 = 7!

Number of ways in which balls 1, 2 and 3 are placed in box 1,2,3 = 6!

Total number of ways = 9!-(8!+8!+8!-7!-7!-7!+61) = 9!-3*8!+3*7!-6!

need explaination for sentence correction questions

Pv Aaditya

3 years, 5 months ago

Hi Rakesh, please let us know if you have any specific questions in mind.

Is answering a posted question restricted to a few members? I ask as i don't see a way to do that myself.

Pv Aaditya

3 years, 5 months ago

Hi Vipul, no anybody can answer the question. Is there any specific question that you had a trouble answering?

time and distance short test 6 last question

Pv Aaditya

3 years, 5 months ago

Let the distance between A and B be d.

Speed of superfast train = 2E and speed of passenger train = E/2

So, d/2E + d/(E/2) = 1 => d = 2E/5

Let the speed of the passenger train in the second case be x

In the second case, d/4E + d/x = 2/3

Substituting for d and solving for x, we get, x = 12E/17

So, ratio of speeds = 12E/17 / 4E = 3 : 17, which is approximately equal to 1 : 6

F or I or J: "Other countries have already seen the benefit of investing in education and a younger generation, but it is no small step for a country whose majority still live in abject property." Acc to me its an Inference as the stmt derives an inference that it is no small step due to the fact that majority still live in abject property..But the official answer --Judgement

Pv Aaditya

3 years, 5 months ago

Hi Vipul, the key words that determine whether this sentence is an inference or judgement are "no small step for a country whose majority live in abject poverty". The words 'small', 'abject' etc. are opinions of the author. So, the statement is a judgement.

all the natural numbers less than n are written on the blackboard and when one of the number is erased the average of remaining numbers is found out to be 28.what is the erased number????can u please explain in detail???

Pv Aaditya

3 years, 5 months ago

Hi Ramakant, can you please check if all the information required is present in the question?

One possible solution: Let the numbers be 1 to 56. 56 is erased. So, the set of numbers is 1 to 55 and the average is 28.

How do I solve para jumbles?

Pv Aaditya

3 years, 5 months ago

How to prepare for Para Jumbles:

Practice, practice, practice!: A student can improve a lot in para jumbles by practicing. You get used to the process of looking for connectives and joining different threads together into a coherent chain of thought

Read: The skills used in Para Jumbles are the same as the skills used in Reading Comprehension. Therefore you should get into the habit of reading everyday. Read opinion articles in any of the major dailies. Analyze the information given in them and summarize each paragraph

Important points to note:

Main point of the paragraph: Read all sentences. Try to understand what is the main point of the paragraph. Find the sentence where the subject of the paragraph - person, event or idea is first introduced. This sentence is likely to be the first sentence or would at least be in the first few sentences.

Try to find verbal connectives: Verbal connectives like but, on the other hand, nevertheless etc provide important clues regarding the paragraph. If you find a negative connective like but, nevertheless etc find the idea being rejected in that statement. The line that states this idea would immediately precede this line. However, a note of caution : Some paragraphs can begin with connectives like However, but etc.

Try to find logical connectives: When a statement lists two reasons, or two concerns or any enumeration of this sort find the the two sentences with the reasons. These sentences should follow the line.

Analogies: If an analogy is given it should precede the real life example. For example if the author states that when a stone is dropped in water, its ripples are felt for some time after the event. If there is a sentence which gives the example of how we are still feeling the ripples of a great event, this line with the real life example must be after the line with the analogy

Definition of subject: Find lines where pronouns like he, it are used. They should immediately follow lines where this noun is defined.