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Question:     Find the average of odd numbers from 5 to 1047


Correct Answer  526

Solution And Explanation

Solution

Method (1) to find the average of the odd numbers from 5 to 1047

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

The odd numbers from 5 to 1047 are

5, 7, 9, . . . . 1047

After observing the above list of the odd numbers from 5 to 1047 we find that the difference between two consecutive terms are equal. This means the list of the odd numbers from 5 to 1047 form an Arithmetic Series.

In the Arithmetic Series of the odd numbers from 5 to 1047

The First Term (a) = 5

The Common Difference (d) = 2

And the last term (ℓ) = 1047

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 odd numbers from 5 to 1047

= 5 + 1047/2

= 1052/2 = 526

Thus, the average of the odd numbers from 5 to 1047 = 526 Answer

Method (2) to find the average of the odd numbers from 5 to 1047

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

The odd numbers from 5 to 1047 are

5, 7, 9, . . . . 1047

The odd numbers from 5 to 1047 form an Arithmetic Series in which

The First Term (a) = 5

The Common Difference (d) = 2

And the last term (ℓ) = 1047

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 odd numbers from 5 to 1047

1047 = 5 + (n – 1) × 2

⇒ 1047 = 5 + 2 n – 2

⇒ 1047 = 5 – 2 + 2 n

⇒ 1047 = 3 + 2 n

After transposing 3 to LHS

⇒ 1047 – 3 = 2 n

⇒ 1044 = 2 n

After rearranging the above expression

⇒ 2 n = 1044

After transposing 2 to RHS

⇒ n = 1044/2

⇒ n = 522

Thus, the number of terms of odd numbers from 5 to 1047 = 522

This means 1047 is the 522th term.

Finding the sum of the given odd numbers from 5 to 1047

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 odd numbers from 5 to 1047

= 522/2 (5 + 1047)

= 522/2 × 1052

= 522 × 1052/2

= 549144/2 = 274572

Thus, the sum of all terms of the given odd numbers from 5 to 1047 = 274572

And, the total number of terms = 522

Since, the average of the given numbers

= Sum of the given numbers/Total number of given numbers

Thus, the average of the given odd numbers from 5 to 1047

= 274572/522 = 526

Thus, the average of the given odd numbers from 5 to 1047 = 526 Answer


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