Question:
Find the average of odd numbers from 7 to 289
Correct Answer
148
Solution And Explanation
Solution
Method (1) to find the average of the odd numbers from 7 to 289
Shortcut Trick to find the average of the given continuous odd numbers
The odd numbers from 7 to 289 are
7, 9, 11, . . . . 289
After observing the above list of the odd numbers from 7 to 289 we find that the difference between two consecutive terms are equal. This means the list of the odd numbers from 7 to 289 form an Arithmetic Series.
In the Arithmetic Series of the odd numbers from 7 to 289
The First Term (a) = 7
The Common Difference (d) = 2
And the last term (ℓ) = 289
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 7 to 289
= 7 + 289/2
= 296/2 = 148
Thus, the average of the odd numbers from 7 to 289 = 148 Answer
Method (2) to find the average of the odd numbers from 7 to 289
Finding the average of given continuous odd numbers after finding their sum
The odd numbers from 7 to 289 are
7, 9, 11, . . . . 289
The odd numbers from 7 to 289 form an Arithmetic Series in which
The First Term (a) = 7
The Common Difference (d) = 2
And the last term (ℓ) = 289
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 7 to 289
289 = 7 + (n – 1) × 2
⇒ 289 = 7 + 2 n – 2
⇒ 289 = 7 – 2 + 2 n
⇒ 289 = 5 + 2 n
After transposing 5 to LHS
⇒ 289 – 5 = 2 n
⇒ 284 = 2 n
After rearranging the above expression
⇒ 2 n = 284
After transposing 2 to RHS
⇒ n = 284/2
⇒ n = 142
Thus, the number of terms of odd numbers from 7 to 289 = 142
This means 289 is the 142th term.
Finding the sum of the given odd numbers from 7 to 289
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 7 to 289
= 142/2 (7 + 289)
= 142/2 × 296
= 142 × 296/2
= 42032/2 = 21016
Thus, the sum of all terms of the given odd numbers from 7 to 289 = 21016
And, the total number of terms = 142
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 7 to 289
= 21016/142 = 148
Thus, the average of the given odd numbers from 7 to 289 = 148 Answer
Similar Questions
(1) Find the average of the first 3648 even numbers.
(2) Find the average of odd numbers from 11 to 255
(3) Find the average of even numbers from 10 to 1976
(4) Find the average of the first 961 odd numbers.
(5) Find the average of the first 822 odd numbers.
(6) What is the average of the first 1569 even numbers?
(7) Find the average of even numbers from 8 to 414
(8) Find the average of odd numbers from 5 to 633
(9) Find the average of odd numbers from 11 to 1029
(10) What will be the average of the first 4692 odd numbers?