Question:
Find the average of odd numbers from 11 to 19
Correct Answer
15
Solution And Explanation
Solution
Method (1) to find the average of the odd numbers from 11 to 19
Shortcut Trick to find the average of the given continuous odd numbers
The odd numbers from 11 to 19 are
11, 13, 15, . . . . 19
After observing the above list of the odd numbers from 11 to 19 we find that the difference between two consecutive terms are equal. This means the list of the odd numbers from 11 to 19 form an Arithmetic Series.
In the Arithmetic Series of the odd numbers from 11 to 19
The First Term (a) = 11
The Common Difference (d) = 2
And the last term (ℓ) = 19
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 11 to 19
= 11 + 19/2
= 30/2 = 15
Thus, the average of the odd numbers from 11 to 19 = 15 Answer
Method (2) to find the average of the odd numbers from 11 to 19
Finding the average of given continuous odd numbers after finding their sum
The odd numbers from 11 to 19 are
11, 13, 15, . . . . 19
The odd numbers from 11 to 19 form an Arithmetic Series in which
The First Term (a) = 11
The Common Difference (d) = 2
And the last term (ℓ) = 19
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 11 to 19
19 = 11 + (n – 1) × 2
⇒ 19 = 11 + 2 n – 2
⇒ 19 = 11 – 2 + 2 n
⇒ 19 = 9 + 2 n
After transposing 9 to LHS
⇒ 19 – 9 = 2 n
⇒ 10 = 2 n
After rearranging the above expression
⇒ 2 n = 10
After transposing 2 to RHS
⇒ n = 10/2
⇒ n = 5
Thus, the number of terms of odd numbers from 11 to 19 = 5
This means 19 is the 5th term.
Finding the sum of the given odd numbers from 11 to 19
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 11 to 19
= 5/2 (11 + 19)
= 5/2 × 30
= 5 × 30/2
= 150/2 = 75
Thus, the sum of all terms of the given odd numbers from 11 to 19 = 75
And, the total number of terms = 5
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 11 to 19
= 75/5 = 15
Thus, the average of the given odd numbers from 11 to 19 = 15 Answer
Similar Questions
(1) What is the average of the first 1338 even numbers?
(2) Find the average of even numbers from 4 to 614
(3) What will be the average of the first 4042 odd numbers?
(4) Find the average of the first 4300 even numbers.
(5) Find the average of odd numbers from 3 to 1075
(6) Find the average of the first 3906 odd numbers.
(7) What is the average of the first 1812 even numbers?
(8) Find the average of even numbers from 8 to 594
(9) Find the average of the first 2281 even numbers.
(10) Find the average of the first 2325 odd numbers.