There are 4 books on fairy tales, 5 novels and 3 plays. In how many ways can you arrange these so that books on fairy tales are together, novels are together and plays are together and in the order, books on fairytales, novels and plays ?

Correct Answer: 164

Explanation:

For a triangle, we need 3 non-collinear points. So with 12 points (when all the 12 are such that any three non-collinear is 12 C 3. But among them 8 points are collinear.

 

If all these 8 points are different we get  8 C 3 triangles as they are collinear.

 

In  12 C 3 triangles, we do not get  8 C 3 triangles

 

Therefore, The number of triangles we get = 12 C 3 - 8 C 3 = 164

Correct Answer: 531

Explanation:

Given in the question that, there are 7 boys and 6 girls. 

Team members = 5

Now, required number of ways in which a team of 5 having atleast 3 girls in the team = 

$$\begin{gathered} 6 C 3 x 7 C 2 + 6 C 4 x 7 C 1 + 6 C 5 \\ = 6 x 5 x 4 3 x 2 x 1 x 7 x 6 2 x 1 + 6 x 5 x 4 x 3 4 x 3 x 2 x 1 x 7 + 6 x 5 x 4 x 3 x 2 5 x 4 x 3 x 2 x 1 \\ = 420 + 105 + 6 \\ = 531 . \end{gathered}$$

Correct Answer: 6! x ?P?

Explanation:

We can initially arrange the six boys in 6! ways.
Having done this, now three are seven places and six girls to be arranged. This can be done in ?P? ways.

Hence required number of ways = 6! x ?P?

Correct Answer: 243

Explanation:

Digits are 0,1,2,3,4,5,6,7,8,9. So no. of digits are 10

 

First all possible case => 9(0 excluded) x 10 x 10 = 900

 

Second no repetition allowed =>9 x 9 x 8 = 648

 

Third all digits are same => 9 (111,222,333,444,555,666,777,888,999)

 

Three digit numbers where two of the three digits are same = 900 - 648 - 9 = 243 ;

Correct Answer: 36

Explanation:

Given there are 9 flavours of ice creams.

 

Each child takes the combination of two flavours and no two children will have the same combination

 

This can be done by  ways i.e children.

 

Number of children= C 2 9  = 9 x 8 / 1x 2 = 36.

Correct Answer: 100

Explanation:

1 million distinct 3 digit initials are needed.

 

Let the number of required alphabets in the language be ?n?.

 

Therefore, using ?n? alphabets we can form n * n * n =  n 3 distinct 3 digit initials.

 

Note distinct initials is different from initials where the digits are different.

 

For instance, AAA and BBB are acceptable combinations in the case of distinct initials while they are not permitted when the digits of the initials need to be different.

 

This  n 3 different initials = 1 million 

i.e.  n 3 = 10 6  (1 million = 10 6)

  => n =  10 2 = 100

 

Hence, the language needs to have a minimum of 100 alphabets to achieve the objective.

Correct Answer: 14

Explanation:

7 C 2- 7 = 14

Correct Answer: 455

Explanation:

There are 15 dots in total,and to make a triangle we need to select any three of those dots.

 

So, 15 C 3 = 455

Correct Answer: 42

Explanation:

The question requires you to find number of the outcomes in which at most 3 coins turn up as heads.

i.e., 0 coins turn heads or 1 coin turns head or 2 coins turn heads or 3 coins turn heads.

 

The number of outcomes in which 0 coins turn heads is  6 C 0=1 

The number of outcomes in which 1 coin turns head is = 6 C 1=6 

The number of outcomes in which 2 coins turn heads is 6 C 2=15 

The number of outcomes in which 3 coins turn heads is 6 C 3=20

 

Therefore, total number of outcomes =1+6+15+20= 42 outcomes

Correct Answer: 70

Explanation:

All the boxes contain distinct number of chocolates.
For each combination of 4 out of 8 boxes, the box with the greatest number has to be given to the first person, the box with the second highest to the second person and so on.

 

The number of ways of giving 4 boxes to the 4 person is: 8 C 4= 70