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Average
Math MCQs


Question :    Find the average of even numbers from 8 to 414


Correct Answer  211

Solution & Explanation

Solution

Method (1) to find the average of the even numbers from 8 to 414

Shortcut Trick to find the average of the given continuous even numbers

The even numbers from 8 to 414 are

8, 10, 12, . . . . 414

After observing the above list of the even numbers from 8 to 414 we find that the difference between two consecutive terms are equal. This means the list of the even numbers from 8 to 414 form an Arithmetic Series.

In the Arithmetic Series of the even numbers from 8 to 414

The First Term (a) = 8

The Common Difference (d) = 2

And the last term (ℓ) = 414

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 414

= 8 + 414/2

= 422/2 = 211

Thus, the average of the even numbers from 8 to 414 = 211 Answer

Method (2) to find the average of the even numbers from 8 to 414

Finding the average of given continuous even numbers after finding their sum

The even numbers from 8 to 414 are

8, 10, 12, . . . . 414

The even numbers from 8 to 414 form an Arithmetic Series in which

The First Term (a) = 8

The Common Difference (d) = 2

And the last term (ℓ) = 414

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 414

414 = 8 + (n – 1) × 2

⇒ 414 = 8 + 2 n – 2

⇒ 414 = 8 – 2 + 2 n

⇒ 414 = 6 + 2 n

After transposing 6 to LHS

⇒ 414 – 6 = 2 n

⇒ 408 = 2 n

After rearranging the above expression

⇒ 2 n = 408

After transposing 2 to RHS

⇒ n = 408/2

⇒ n = 204

Thus, the number of terms of even numbers from 8 to 414 = 204

This means 414 is the 204th term.

Finding the sum of the given even numbers from 8 to 414

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 414

= 204/2 (8 + 414)

= 204/2 × 422

= 204 × 422/2

= 86088/2 = 43044

Thus, the sum of all terms of the given even numbers from 8 to 414 = 43044

And, the total number of terms = 204

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 414

= 43044/204 = 211

Thus, the average of the given even numbers from 8 to 414 = 211 Answer


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