Question

Find the unit digit of 1781+2781+3781+.........9781

Answer 1

Answer:

47

Step-by-step explanation:

first first two numbers are 17,27 ,37 after,47

Answer 2

Given:

There are sum of given number 1781+2781+3781+...+9781

To Find:

What is unit digit of sum of number ?

Solution:

Again write the all number with addition, we get:

1781+2781+3781+.........9781

Here we observed that it is sum of nine numbers:

It is also clear that unit digit of all nine number is 1:

On adding unit digit of all number:

Unit digit of sum of all number = 1+1+1+1+1+1+1+1+1 =9

So unit digit of sum of numbers is 9. This is answer.