Question : Find the average of even numbers from 4 to 774
Correct Answer 389
Solution & Explanation
Solution
Method (1) to find the average of the even numbers from 4 to 774
Shortcut Trick to find the average of the given continuous even numbers
The even numbers from 4 to 774 are
4, 6, 8, . . . . 774
After observing the above list of the even numbers from 4 to 774 we find that the difference between two consecutive terms are equal. This means the list of the even numbers from 4 to 774 form an Arithmetic Series.
In the Arithmetic Series of the even numbers from 4 to 774
The First Term (a) = 4
The Common Difference (d) = 2
And the last term (ℓ) = 774
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 4 to 774
= 4 + 774/2
= 778/2 = 389
Thus, the average of the even numbers from 4 to 774 = 389 Answer
Method (2) to find the average of the even numbers from 4 to 774
Finding the average of given continuous even numbers after finding their sum
The even numbers from 4 to 774 are
4, 6, 8, . . . . 774
The even numbers from 4 to 774 form an Arithmetic Series in which
The First Term (a) = 4
The Common Difference (d) = 2
And the last term (ℓ) = 774
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 4 to 774
774 = 4 + (n – 1) × 2
⇒ 774 = 4 + 2 n – 2
⇒ 774 = 4 – 2 + 2 n
⇒ 774 = 2 + 2 n
After transposing 2 to LHS
⇒ 774 – 2 = 2 n
⇒ 772 = 2 n
After rearranging the above expression
⇒ 2 n = 772
After transposing 2 to RHS
⇒ n = 772/2
⇒ n = 386
Thus, the number of terms of even numbers from 4 to 774 = 386
This means 774 is the 386th term.
Finding the sum of the given even numbers from 4 to 774
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 4 to 774
= 386/2 (4 + 774)
= 386/2 × 778
= 386 × 778/2
= 300308/2 = 150154
Thus, the sum of all terms of the given even numbers from 4 to 774 = 150154
And, the total number of terms = 386
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 4 to 774
= 150154/386 = 389
Thus, the average of the given even numbers from 4 to 774 = 389 Answer
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