Question : Find the average of odd numbers from 15 to 357
Correct Answer 186
Solution & Explanation
Solution
Method (1) to find the average of the odd numbers from 15 to 357
Shortcut Trick to find the average of the given continuous odd numbers
The odd numbers from 15 to 357 are
15, 17, 19, . . . . 357
After observing the above list of the odd numbers from 15 to 357 we find that the difference between two consecutive terms are equal. This means the list of the odd numbers from 15 to 357 form an Arithmetic Series.
In the Arithmetic Series of the odd numbers from 15 to 357
The First Term (a) = 15
The Common Difference (d) = 2
And the last term (ℓ) = 357
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 15 to 357
= 15 + 357/2
= 372/2 = 186
Thus, the average of the odd numbers from 15 to 357 = 186 Answer
Method (2) to find the average of the odd numbers from 15 to 357
Finding the average of given continuous odd numbers after finding their sum
The odd numbers from 15 to 357 are
15, 17, 19, . . . . 357
The odd numbers from 15 to 357 form an Arithmetic Series in which
The First Term (a) = 15
The Common Difference (d) = 2
And the last term (ℓ) = 357
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 15 to 357
357 = 15 + (n – 1) × 2
⇒ 357 = 15 + 2 n – 2
⇒ 357 = 15 – 2 + 2 n
⇒ 357 = 13 + 2 n
After transposing 13 to LHS
⇒ 357 – 13 = 2 n
⇒ 344 = 2 n
After rearranging the above expression
⇒ 2 n = 344
After transposing 2 to RHS
⇒ n = 344/2
⇒ n = 172
Thus, the number of terms of odd numbers from 15 to 357 = 172
This means 357 is the 172th term.
Finding the sum of the given odd numbers from 15 to 357
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 15 to 357
= 172/2 (15 + 357)
= 172/2 × 372
= 172 × 372/2
= 63984/2 = 31992
Thus, the sum of all terms of the given odd numbers from 15 to 357 = 31992
And, the total number of terms = 172
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 15 to 357
= 31992/172 = 186
Thus, the average of the given odd numbers from 15 to 357 = 186 Answer
Similar Questions
(1) Find the average of odd numbers from 15 to 1397
(2) Find the average of the first 2886 odd numbers.
(3) Find the average of odd numbers from 9 to 1175
(4) Find the average of odd numbers from 11 to 101
(5) What is the average of the first 1271 even numbers?
(6) Find the average of the first 990 odd numbers.
(7) Find the average of odd numbers from 11 to 649
(8) What is the average of the first 1757 even numbers?
(9) Find the average of the first 2006 even numbers.
(10) What will be the average of the first 4451 odd numbers?