Question:
Find the average of even numbers from 8 to 218
Correct Answer
113
Solution And Explanation
Solution
Method (1) to find the average of the even numbers from 8 to 218
Shortcut Trick to find the average of the given continuous even numbers
The even numbers from 8 to 218 are
8, 10, 12, . . . . 218
After observing the above list of the even numbers from 8 to 218 we find that the difference between two consecutive terms are equal. This means the list of the even numbers from 8 to 218 form an Arithmetic Series.
In the Arithmetic Series of the even numbers from 8 to 218
The First Term (a) = 8
The Common Difference (d) = 2
And the last term (ℓ) = 218
The average of the numbers forming an Arithmetic Series
= The first term (a) + The last term (ℓ)/2
⇒ The average of numbers forming an Arithmetic Series = a + ℓ/2
Thus, the average of the even numbers from 8 to 218
= 8 + 218/2
= 226/2 = 113
Thus, the average of the even numbers from 8 to 218 = 113 Answer
Method (2) to find the average of the even numbers from 8 to 218
Finding the average of given continuous even numbers after finding their sum
The even numbers from 8 to 218 are
8, 10, 12, . . . . 218
The even numbers from 8 to 218 form an Arithmetic Series in which
The First Term (a) = 8
The Common Difference (d) = 2
And the last term (ℓ) = 218
The Average of the given numbers
= Sum of the given numbers/Total number of given numbers
Thus, to find the average of the given numbers, first, we need to find their sum and the total number of given numbers
Finding the number of terms
For an Arithmetic Series, the nth term
an = a + (n – 1) d
Where
a = First term
d = Common difference
n = number of terms
an = nth term
Thus, for the given series of the even numbers from 8 to 218
218 = 8 + (n – 1) × 2
⇒ 218 = 8 + 2 n – 2
⇒ 218 = 8 – 2 + 2 n
⇒ 218 = 6 + 2 n
After transposing 6 to LHS
⇒ 218 – 6 = 2 n
⇒ 212 = 2 n
After rearranging the above expression
⇒ 2 n = 212
After transposing 2 to RHS
⇒ n = 212/2
⇒ n = 106
Thus, the number of terms of even numbers from 8 to 218 = 106
This means 218 is the 106th term.
Finding the sum of the given even numbers from 8 to 218
The sum of all terms (S) in an Arithmetic Series
= n/2 (a + ℓ)
Where, n = number of terms
a = First term
And, ℓ = Last term
Thus, the sum of all terms (S) of the given even numbers from 8 to 218
= 106/2 (8 + 218)
= 106/2 × 226
= 106 × 226/2
= 23956/2 = 11978
Thus, the sum of all terms of the given even numbers from 8 to 218 = 11978
And, the total number of terms = 106
Since, the average of the given numbers
= Sum of the given numbers/Total number of given numbers
Thus, the average of the given even numbers from 8 to 218
= 11978/106 = 113
Thus, the average of the given even numbers from 8 to 218 = 113 Answer
Similar Questions
(1) Find the average of the first 3817 even numbers.
(2) Find the average of the first 2124 even numbers.
(3) Find the average of even numbers from 6 to 558
(4) Find the average of odd numbers from 11 to 399
(5) Find the average of odd numbers from 15 to 969
(6) Find the average of the first 3538 odd numbers.
(7) Find the average of odd numbers from 13 to 1105
(8) Find the average of odd numbers from 13 to 241
(9) Find the average of the first 4058 even numbers.
(10) What will be the average of the first 4827 odd numbers?