Question

The number of ways in which four letters can put in four addressed envelopes so that no letter goes into the envelope meant for it is :

- 7
- 9
- 4
- 2

Hint:

### First we will find the total number of ways of putting letters in the envelope, then we will find the number of ways of putting 1 letter, 2 letters, 3 letters and 4 letters in the right envelope respectively. At last, to find the total no, of ways when no letter will be in the right envelope we will subtract the number of ways of putting 1 letter, 2 letters, 3 letters and 4 letters in the right envelope respectively from total number of ways.

## The correct answer is: 9

### Total number of ways of putting 4 letters in 4 envelopes = 4! =24

Now, number of ways of putting only 1 letter in the right envelope= =8

number of ways of putting only 2 letters in the right envelopes ==6

number of ways of putting 3 letters in the right envelope= 0, as when we will put three letters in the right envelope the last will automatically go in the right place.

number of ways of putting 4 letters in the right envelope= 1

So, the number of ways in which four letters can put in four addressed envelopes so that no letter goes into the envelope meant for it =24-(8+6+0+1)=24-15=9

### Related Questions to study

### In the given figure of the heart which of the labelled part (1, 2, 3, 4, 5) carries oxygenated blood?

### In the given figure of the heart which of the labelled part (1, 2, 3, 4, 5) carries oxygenated blood?

### The given figure shows an angiogram of the coronary blood vessel. Which one of the following statements correctly describes, what is being done?

### The given figure shows an angiogram of the coronary blood vessel. Which one of the following statements correctly describes, what is being done?

There are 3 letters and 3 addressed envelopes corresponding to them. The number of ways in which the letters be placed in the envelopes so that no letter is in the right envelope is:

There are 3 letters and 3 addressed envelopes corresponding to them. The number of ways in which the letters be placed in the envelopes so that no letter is in the right envelope is:

### Match Column - I with Column - II and select the correct option from the codes give below.

### Match Column - I with Column - II and select the correct option from the codes give below.

The sum of all the numbers formed by taking all the digits from 3,4,5,6,7 is:

The sum of all the numbers formed by taking all the digits from 3,4,5,6,7 is:

The sum of all the numbers formed by taking all the digits from 2,3,4,5 is:

The sum of all the numbers formed by taking all the digits from 2,3,4,5 is:

### The number of constant mappings from to is

### The number of constant mappings from to is

### The number of many one functions from is

### The number of many one functions from is

### The number of into functions that can be defined from is

### The number of into functions that can be defined from is

A body moving with velocity v has momentum and kinetic energy numerically equal. What is the value of v?

A body moving with velocity v has momentum and kinetic energy numerically equal. What is the value of v?

The graph between the resistive force F acting on a body and the distance covered by the body is shown in figure. The mass of the body is 25KG and initial velocity is 2 m/s. When the distance covered by the body is 4km, its kinetic energy would be

The graph between the resistive force F acting on a body and the distance covered by the body is shown in figure. The mass of the body is 25KG and initial velocity is 2 m/s. When the distance covered by the body is 4km, its kinetic energy would be

The number of onto functions that can be defined from A={a,b,c,d,e} to {1,2} is

The number of onto functions that can be defined from A={a,b,c,d,e} to {1,2} is

The momentum of a body increases by 20%. The percentage increase in its kinetic energy is

The momentum of a body increases by 20%. The percentage increase in its kinetic energy is

Two spheres A and B of masses M_{1} and M_{2} respectively collide. A is at rest initially and B is moving with velocity V along X-axis. After collision has a velocity in a direction perpendicular to the original direction. The mass moves after collision in the direction

Two spheres A and B of masses M_{1} and M_{2} respectively collide. A is at rest initially and B is moving with velocity V along X-axis. After collision has a velocity in a direction perpendicular to the original direction. The mass moves after collision in the direction

A block of mass 10 kg slides down a rough slope which is inclined at to the horizontal. The coefficient of sliding friction is 0.30. When the block has slide 5 m, the work done on the block by the force of friction is nearly

A block of mass 10 kg slides down a rough slope which is inclined at to the horizontal. The coefficient of sliding friction is 0.30. When the block has slide 5 m, the work done on the block by the force of friction is nearly