From numbers 1 to 100 what is the probability of getting even numbers that add up the digits to 9

The sum of even numbers from 2 to infinity can be obtained easily, using Arithmetic Progression as well as using the formula of sum of all natural numbers. We know that the even numbers are the numbers, which are completely divisible by 2. They are 2, 4, 6, 8,10, 12,14, 16 and so on. Now, we need to find the total of these numbers. Also, find sum of odd numbers here.

Learn about even numbers here.

Basically, the formula to find the sum of even numbers is n(n+1), where n is the natural number. We can find this formula using the formula of the sum of natural numbers, such as:

S = 1 + 2+3+4+5+6+7…+n

S= n(n+1)/2

To find the sum of consecutive even numbers, we need to multiply the above formula by 2. Hence,

Se = n(n+1)

Let us derive this formula using AP.

Sum of Even Numbers Formula Using AP

Let the sum of first n even numbers is Sn

Sn = 2+4+6+8+10+…………………..+(2n) ……. (1)

By Arithmetic Progression, we know, for any sequence, the sum of numbers is given by;

Sn=1/2×n[2a+(n-1)d] ……..(2)

Where,

n = number of digits in the series

a = First term of an A.P

d= Common difference in an A.P

Therefore, if we put the values in equation 2 with respect to equation 1, such as;

a=2 , d = 2

Let, last term, l = (2n)

So, the sum will be:

Sn = ½ n[2.2+(n-1)2]

Sn = n/2[4+2n-2]

Sn = n/2[2+2n]

Sn = n(n+1)

Sum of n even numbers = n(n+1)

Sum of First Ten Even numbers

Below is the table for the sum of 1 to 10 consecutive even numbers.

Number of consecutive even numbers (n) Sum of even numbers (Sn = n (n+1)) Recheck
1 1(1+1)=1×2=2 2
2 2(2+1) = 2×3 = 6 2+4 = 6
3 3(3+1)=3×4 = 12 2+4+6 = 12
4 4(4+1) = 4 x 5 = 20 2+4+6+8=20
5 5(5+1) = 5 x 6 = 30 2+4+6+8+10 = 30
6 6(6+1) = 6 x 7 = 42 2+4+6+8+10+12 = 42
7 7(7+1) = 7×8 = 56 2+4+6+8+10+12+14 = 56
8 8(8+1) = 8 x 9 = 72 2+4+6+8+10+12+14+16=72
9 9(9+1) = 9 x 10 = 90 2+4+6+8+10+12+14+16+18=90
10 10(10+1) = 10 x 11 =110 2+4+6+8+10+12+14+16+18+20=110

Also, read:

  • Sum Of N Terms
  • Sum Of Squares

Solved Examples

Question 1: What is the sum of even numbers from 1 to 50?

Solution: We know that, from 1 to 50, there are 25 even numbers.

Thus, n = 25

By the formula of sum of even numbers we know;

Sn = n(n+1)

Sn = 25(25+1) = 25 x 26 = 650

Question 2: What is the sum of the first 100 even numbers?

Solution: We know that, from 1 to 100, there are 50 even numbers.

Thus, n = 50

By the formula of sum of even numbers we know;

Sn = n(n+1)

Sn = 50(50+1) = 50 x 51 = 2550

Question 3: Find the sum of even numbers from 1 to 200?

Solution: We know that, from 1 to 200, there are 100 even numbers.

Thus, n =100

By the formula of the sum of even numbers we know;

Sn = n(n+1)

Sn = 100(100+1) = 100 x 101 = 10100

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All the even and odd numbers between 1 and 100 are discussed here.

What are the even numbers from 1 to 100?

The even numbers from 1 to 100 are:

2             4             6             8           1012           14           16           18           2022           24           26           28           3032           34           36           38           4042           44           46           48           5052           54           56           58           6062           64           66           68           7072           74           76           78           8082           84           86           88           9092           94           96           98           100

What are the odd numbers from 1 to 100?

The odd numbers from 1 to 100 are:

1             3             5             7             911           13           15           17           1921           23           25           27           2931           33           35           37           3941           43           45           47           4951           53           55           57           5961           63           65           67           6971           73           75           77           7981           83           85           87           8991           93           95           97           99

Even and Odd  Numbers


1. (i) Every number coming after an even number is an odd number12 + 1 = 13 16+1 = 17 176 + 1 = 177 216 + 1 = 217

(ii) Every number coming after an odd number is an even number15 + 1 = 16 19 + 1 = 20 205 + 1 = 206

419 + 1 = 420

2. Every number having 2, 4, 6, 8 and 0 at its one’s place is divisible by 2 and hence, an even number.

3. No number having 3, 5, 7 and 9 at its one's place is divisible by 2 and hence, an odd number.

4. All the even and odd numbers are whole numbers.

Related Concept

Factors and Multiples by using Multiplication Facts

Factors and Multiples by using Division Facts

Multiples

Properties of Multiples

Examples on Multiples

Factors

Factor Tree Method

Properties of Factors

Examples on Factors

Even and Odd Numbers

Even and Odd Numbers Between 1 and 100

Examples on Even and Odd Numbers

4th Grade Math Activities

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