Question

find the sum of all the natural numbers from 10 to 20 ?

Answer 1

Sum of the first n natural numbers is n(n+1) /2

the sum of first 20 natural numbers =20*21/2=210

the sum of first 9 is 9*10/2=45

Then the sum of the numbers from 10 to 20 is

sum of first 20 numbers -sum of first 9 numbers= 210-45=165

Answer 2

Answer:

The sum of all the natural numbers from 10 to 20 is 165.

Step-by-step explanation:

We need to find the sum of all the natural numbers from 10 till 20.

That is:

10 + 11 + 12 + ... + 20.

We will use the formula:

S = n / 2[2 a + (n − 1) × d]

where:

n = 11

a = 10

d = 1

S = 11 / 2 [ 2(10) + (11 - 1) × 1]

S  =11 / 2 [ 20 + 10]

S = 11 / 2 (30)

S = 11 × 15

S = 165

Therefore, the sum of all the natural numbers from 10 to 20 is 165.

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