Question : Find the average of odd numbers from 9 to 1305
Correct Answer 657
Solution & Explanation
Solution
Method (1) to find the average of the odd numbers from 9 to 1305
Shortcut Trick to find the average of the given continuous odd numbers
The odd numbers from 9 to 1305 are
9, 11, 13, . . . . 1305
After observing the above list of the odd numbers from 9 to 1305 we find that the difference between two consecutive terms are equal. This means the list of the odd numbers from 9 to 1305 form an Arithmetic Series.
In the Arithmetic Series of the odd numbers from 9 to 1305
The First Term (a) = 9
The Common Difference (d) = 2
And the last term (ℓ) = 1305
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 1305
= 9 + 1305/2
= 1314/2 = 657
Thus, the average of the odd numbers from 9 to 1305 = 657 Answer
Method (2) to find the average of the odd numbers from 9 to 1305
Finding the average of given continuous odd numbers after finding their sum
The odd numbers from 9 to 1305 are
9, 11, 13, . . . . 1305
The odd numbers from 9 to 1305 form an Arithmetic Series in which
The First Term (a) = 9
The Common Difference (d) = 2
And the last term (ℓ) = 1305
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 1305
1305 = 9 + (n – 1) × 2
⇒ 1305 = 9 + 2 n – 2
⇒ 1305 = 9 – 2 + 2 n
⇒ 1305 = 7 + 2 n
After transposing 7 to LHS
⇒ 1305 – 7 = 2 n
⇒ 1298 = 2 n
After rearranging the above expression
⇒ 2 n = 1298
After transposing 2 to RHS
⇒ n = 1298/2
⇒ n = 649
Thus, the number of terms of odd numbers from 9 to 1305 = 649
This means 1305 is the 649th term.
Finding the sum of the given odd numbers from 9 to 1305
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 1305
= 649/2 (9 + 1305)
= 649/2 × 1314
= 649 × 1314/2
= 852786/2 = 426393
Thus, the sum of all terms of the given odd numbers from 9 to 1305 = 426393
And, the total number of terms = 649
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 1305
= 426393/649 = 657
Thus, the average of the given odd numbers from 9 to 1305 = 657 Answer
Similar Questions
(1) Find the average of the first 3142 odd numbers.
(2) Find the average of even numbers from 8 to 638
(3) Find the average of even numbers from 6 to 1856
(4) Find the average of odd numbers from 7 to 1351
(5) Find the average of odd numbers from 3 to 1055
(6) What will be the average of the first 4229 odd numbers?
(7) What will be the average of the first 4718 odd numbers?
(8) Find the average of even numbers from 10 to 1502
(9) Find the average of odd numbers from 15 to 401
(10) Find the average of even numbers from 12 to 156