###### Asked in Math and Arithmetic

Math and Arithmetic

# What is the sum of first twenty counting numbers?

## Answer

###### Wiki User

###### July 30, 2014 3:21PM

The sum of first 20 counting numbers is 190.

## Related Questions

###### Asked in Math and Arithmetic, Algebra

### What is the sum of the first one hundred counting number?

Here is a nice way to see and remember this. Look at the sum of
the first 5 counting number Write them as 1,2,3,4,5 Now write them
backward as 5,4,3,2,1 Place the second list under the first list
and add the numbers in each column. Each sum is 6 and there are 5
sums. However, you counted the numbers twice since you wrote the
list both ways. So the sum of the first 5 numbers is 5x6/2 In
general the sum of the first n natural numbers is n(n+1)/2 So the
sum of the first 100 numbers is 100x101/2=50x101=5050 This formula
can also be proved by induction and several other ways.

###### Asked in Math and Arithmetic

### What is the sum of the first twenty counting numbers?

20*(20+1)/2 = 210
If you want to see how this works, or even the beauty in
numbers, you can do so in MS Excel. In cell A1 put "=ROW()" B1:
"=SUM(A$1:A1)" C1: "B1/A1". Then, select and copy those three
cells. Paste the content in any number of rows down in those three
columns.
Be sure to note the following patterns:
Every 20 numbers, the one's digit repeats itself in the sum
column (B column),
The sum of the first 10 numbers is 55, the first 100 is 5050,
1000 is 500500.