Question:
Find the average of odd numbers from 15 to 1767
Correct Answer
891
Solution And Explanation
Solution
Method (1) to find the average of the odd numbers from 15 to 1767
Shortcut Trick to find the average of the given continuous odd numbers
The odd numbers from 15 to 1767 are
15, 17, 19, . . . . 1767
After observing the above list of the odd numbers from 15 to 1767 we find that the difference between two consecutive terms are equal. This means the list of the odd numbers from 15 to 1767 form an Arithmetic Series.
In the Arithmetic Series of the odd numbers from 15 to 1767
The First Term (a) = 15
The Common Difference (d) = 2
And the last term (ℓ) = 1767
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 15 to 1767
= 15 + 1767/2
= 1782/2 = 891
Thus, the average of the odd numbers from 15 to 1767 = 891 Answer
Method (2) to find the average of the odd numbers from 15 to 1767
Finding the average of given continuous odd numbers after finding their sum
The odd numbers from 15 to 1767 are
15, 17, 19, . . . . 1767
The odd numbers from 15 to 1767 form an Arithmetic Series in which
The First Term (a) = 15
The Common Difference (d) = 2
And the last term (ℓ) = 1767
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 15 to 1767
1767 = 15 + (n – 1) × 2
⇒ 1767 = 15 + 2 n – 2
⇒ 1767 = 15 – 2 + 2 n
⇒ 1767 = 13 + 2 n
After transposing 13 to LHS
⇒ 1767 – 13 = 2 n
⇒ 1754 = 2 n
After rearranging the above expression
⇒ 2 n = 1754
After transposing 2 to RHS
⇒ n = 1754/2
⇒ n = 877
Thus, the number of terms of odd numbers from 15 to 1767 = 877
This means 1767 is the 877th term.
Finding the sum of the given odd numbers from 15 to 1767
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 15 to 1767
= 877/2 (15 + 1767)
= 877/2 × 1782
= 877 × 1782/2
= 1562814/2 = 781407
Thus, the sum of all terms of the given odd numbers from 15 to 1767 = 781407
And, the total number of terms = 877
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 15 to 1767
= 781407/877 = 891
Thus, the average of the given odd numbers from 15 to 1767 = 891 Answer
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