Question : Find the average of even numbers from 10 to 550
Correct Answer 280
Solution & Explanation
Solution
Method (1) to find the average of the even numbers from 10 to 550
Shortcut Trick to find the average of the given continuous even numbers
The even numbers from 10 to 550 are
10, 12, 14, . . . . 550
After observing the above list of the even numbers from 10 to 550 we find that the difference between two consecutive terms are equal. This means the list of the even numbers from 10 to 550 form an Arithmetic Series.
In the Arithmetic Series of the even numbers from 10 to 550
The First Term (a) = 10
The Common Difference (d) = 2
And the last term (ℓ) = 550
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 10 to 550
= 10 + 550/2
= 560/2 = 280
Thus, the average of the even numbers from 10 to 550 = 280 Answer
Method (2) to find the average of the even numbers from 10 to 550
Finding the average of given continuous even numbers after finding their sum
The even numbers from 10 to 550 are
10, 12, 14, . . . . 550
The even numbers from 10 to 550 form an Arithmetic Series in which
The First Term (a) = 10
The Common Difference (d) = 2
And the last term (ℓ) = 550
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 10 to 550
550 = 10 + (n – 1) × 2
⇒ 550 = 10 + 2 n – 2
⇒ 550 = 10 – 2 + 2 n
⇒ 550 = 8 + 2 n
After transposing 8 to LHS
⇒ 550 – 8 = 2 n
⇒ 542 = 2 n
After rearranging the above expression
⇒ 2 n = 542
After transposing 2 to RHS
⇒ n = 542/2
⇒ n = 271
Thus, the number of terms of even numbers from 10 to 550 = 271
This means 550 is the 271th term.
Finding the sum of the given even numbers from 10 to 550
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 10 to 550
= 271/2 (10 + 550)
= 271/2 × 560
= 271 × 560/2
= 151760/2 = 75880
Thus, the sum of all terms of the given even numbers from 10 to 550 = 75880
And, the total number of terms = 271
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 10 to 550
= 75880/271 = 280
Thus, the average of the given even numbers from 10 to 550 = 280 Answer
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