### PROBLEM LINK:

**Author:** RAVIT SINGH MALIK

**Editorialist:** RAVIT SINGH MALIK

### DIFFICULTY:

EASY

### PREREQUISITES:

MATHS,NUMBER THEORY

### PROBLEM:

Find the number of ways of selecting one or more items from N distinct things.

### EXPLANATION:

So, Number of ways of selecting one or more items from N distinct things.

nC0 + nC1 + nC2 + nC3 + ------------- + nCn = 2^n

nC1 + -----------------nCn =2^n - nC0

= 2^n – 1 , [ nC0=1]

FOR example,

you need to find number of ways of selecting one or more items from 5 distinct things.

so,

5C0 + 5C1 + 5C2 + 5C3 + 5C4 + 5C5 = 2^5

5C1 + 5C2 + 5C3 + 5C4 + 5C5 =2^n - 5C0

= 2^5 – 1=31

### AUTHOR’S AND TESTER’S SOLUTIONS:

Author’s solution can be found here.