Question:
Find the average of even numbers from 12 to 728
Correct Answer
370
Solution And Explanation
Solution
Method (1) to find the average of the even numbers from 12 to 728
Shortcut Trick to find the average of the given continuous even numbers
The even numbers from 12 to 728 are
12, 14, 16, . . . . 728
After observing the above list of the even numbers from 12 to 728 we find that the difference between two consecutive terms are equal. This means the list of the even numbers from 12 to 728 form an Arithmetic Series.
In the Arithmetic Series of the even numbers from 12 to 728
The First Term (a) = 12
The Common Difference (d) = 2
And the last term (ℓ) = 728
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 12 to 728
= 12 + 728/2
= 740/2 = 370
Thus, the average of the even numbers from 12 to 728 = 370 Answer
Method (2) to find the average of the even numbers from 12 to 728
Finding the average of given continuous even numbers after finding their sum
The even numbers from 12 to 728 are
12, 14, 16, . . . . 728
The even numbers from 12 to 728 form an Arithmetic Series in which
The First Term (a) = 12
The Common Difference (d) = 2
And the last term (ℓ) = 728
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 12 to 728
728 = 12 + (n – 1) × 2
⇒ 728 = 12 + 2 n – 2
⇒ 728 = 12 – 2 + 2 n
⇒ 728 = 10 + 2 n
After transposing 10 to LHS
⇒ 728 – 10 = 2 n
⇒ 718 = 2 n
After rearranging the above expression
⇒ 2 n = 718
After transposing 2 to RHS
⇒ n = 718/2
⇒ n = 359
Thus, the number of terms of even numbers from 12 to 728 = 359
This means 728 is the 359th term.
Finding the sum of the given even numbers from 12 to 728
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 12 to 728
= 359/2 (12 + 728)
= 359/2 × 740
= 359 × 740/2
= 265660/2 = 132830
Thus, the sum of all terms of the given even numbers from 12 to 728 = 132830
And, the total number of terms = 359
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 12 to 728
= 132830/359 = 370
Thus, the average of the given even numbers from 12 to 728 = 370 Answer
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