Question : Find the average of odd numbers from 5 to 309
Correct Answer 157
Solution & Explanation
Solution
Method (1) to find the average of the odd numbers from 5 to 309
Shortcut Trick to find the average of the given continuous odd numbers
The odd numbers from 5 to 309 are
5, 7, 9, . . . . 309
After observing the above list of the odd numbers from 5 to 309 we find that the difference between two consecutive terms are equal. This means the list of the odd numbers from 5 to 309 form an Arithmetic Series.
In the Arithmetic Series of the odd numbers from 5 to 309
The First Term (a) = 5
The Common Difference (d) = 2
And the last term (ℓ) = 309
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 309
= 5 + 309/2
= 314/2 = 157
Thus, the average of the odd numbers from 5 to 309 = 157 Answer
Method (2) to find the average of the odd numbers from 5 to 309
Finding the average of given continuous odd numbers after finding their sum
The odd numbers from 5 to 309 are
5, 7, 9, . . . . 309
The odd numbers from 5 to 309 form an Arithmetic Series in which
The First Term (a) = 5
The Common Difference (d) = 2
And the last term (ℓ) = 309
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 309
309 = 5 + (n – 1) × 2
⇒ 309 = 5 + 2 n – 2
⇒ 309 = 5 – 2 + 2 n
⇒ 309 = 3 + 2 n
After transposing 3 to LHS
⇒ 309 – 3 = 2 n
⇒ 306 = 2 n
After rearranging the above expression
⇒ 2 n = 306
After transposing 2 to RHS
⇒ n = 306/2
⇒ n = 153
Thus, the number of terms of odd numbers from 5 to 309 = 153
This means 309 is the 153th term.
Finding the sum of the given odd numbers from 5 to 309
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 309
= 153/2 (5 + 309)
= 153/2 × 314
= 153 × 314/2
= 48042/2 = 24021
Thus, the sum of all terms of the given odd numbers from 5 to 309 = 24021
And, the total number of terms = 153
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 309
= 24021/153 = 157
Thus, the average of the given odd numbers from 5 to 309 = 157 Answer
Similar Questions
(1) What is the average of the first 275 even numbers?
(2) Find the average of even numbers from 4 to 1882
(3) Find the average of even numbers from 10 to 1084
(4) Find the average of odd numbers from 7 to 993
(5) Find the average of even numbers from 8 to 576
(6) Find the average of the first 959 odd numbers.
(7) Find the average of odd numbers from 15 to 1067
(8) Find the average of odd numbers from 15 to 929
(9) Find the average of the first 3672 even numbers.
(10) Find the average of the first 647 odd numbers.