Question

find the unit digit of the sum of the factorials of the first 100 natural numbers​ pls find it

Answer 1

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♦ First of all we should know what is meant by factorial ?

→ Factorial means the consecutive product of given "n" natural numbers .

And it is represented by n!

By taking example to understand it clearly .

8! = ??

From the definition from above we will write

8! = 8 × 7 × 6 × 5 × 4 × 3 × 2 × 1

= 40320

♦ Now coming back to the question

We have to find out the sum of unit digits of factorials of first 100 natural numbers .

So first we will find out the factorials.

1! = 1

2! = 2

3! = 6

4! = 24

5! = 120

6! = 720

......

♦ We can clearly see that after 4! on the unit place we are getting "0"

As sum of n(0) = 0

Hence the sum of unit digits of first 100 factorials of Natural Numbers

Sum of Unit digits of 1! , 2! , 3! and 4!

= 1 , 2 , 6 , 4

= 1 + 2 + 6 + 4

= 3 + 10

= 13

Hence sum of unit digits of factorials of first 100 natural numbers = 13 .

Answer 2

Step-by-step explanation:

After 4! Unit digit is 0

1+2+6+4=13