Question:
Find the average of odd numbers from 9 to 765
Correct Answer
387
Solution And Explanation
Solution
Method (1) to find the average of the odd numbers from 9 to 765
Shortcut Trick to find the average of the given continuous odd numbers
The odd numbers from 9 to 765 are
9, 11, 13, . . . . 765
After observing the above list of the odd numbers from 9 to 765 we find that the difference between two consecutive terms are equal. This means the list of the odd numbers from 9 to 765 form an Arithmetic Series.
In the Arithmetic Series of the odd numbers from 9 to 765
The First Term (a) = 9
The Common Difference (d) = 2
And the last term (ℓ) = 765
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 9 to 765
= 9 + 765/2
= 774/2 = 387
Thus, the average of the odd numbers from 9 to 765 = 387 Answer
Method (2) to find the average of the odd numbers from 9 to 765
Finding the average of given continuous odd numbers after finding their sum
The odd numbers from 9 to 765 are
9, 11, 13, . . . . 765
The odd numbers from 9 to 765 form an Arithmetic Series in which
The First Term (a) = 9
The Common Difference (d) = 2
And the last term (ℓ) = 765
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 9 to 765
765 = 9 + (n – 1) × 2
⇒ 765 = 9 + 2 n – 2
⇒ 765 = 9 – 2 + 2 n
⇒ 765 = 7 + 2 n
After transposing 7 to LHS
⇒ 765 – 7 = 2 n
⇒ 758 = 2 n
After rearranging the above expression
⇒ 2 n = 758
After transposing 2 to RHS
⇒ n = 758/2
⇒ n = 379
Thus, the number of terms of odd numbers from 9 to 765 = 379
This means 765 is the 379th term.
Finding the sum of the given odd numbers from 9 to 765
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 9 to 765
= 379/2 (9 + 765)
= 379/2 × 774
= 379 × 774/2
= 293346/2 = 146673
Thus, the sum of all terms of the given odd numbers from 9 to 765 = 146673
And, the total number of terms = 379
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 9 to 765
= 146673/379 = 387
Thus, the average of the given odd numbers from 9 to 765 = 387 Answer
Similar Questions
(1) Find the average of odd numbers from 5 to 213
(2) Find the average of even numbers from 10 to 1680
(3) Find the average of the first 2485 even numbers.
(4) Find the average of the first 3524 even numbers.
(5) Find the average of even numbers from 12 to 1654
(6) What will be the average of the first 4021 odd numbers?
(7) What is the average of the first 1484 even numbers?
(8) Find the average of odd numbers from 5 to 1285
(9) Find the average of odd numbers from 7 to 1087
(10) Find the average of the first 2918 even numbers.