Question : Find the average of odd numbers from 7 to 851
Correct Answer 429
Solution & Explanation
Solution
Method (1) to find the average of the odd numbers from 7 to 851
Shortcut Trick to find the average of the given continuous odd numbers
The odd numbers from 7 to 851 are
7, 9, 11, . . . . 851
After observing the above list of the odd numbers from 7 to 851 we find that the difference between two consecutive terms are equal. This means the list of the odd numbers from 7 to 851 form an Arithmetic Series.
In the Arithmetic Series of the odd numbers from 7 to 851
The First Term (a) = 7
The Common Difference (d) = 2
And the last term (ℓ) = 851
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 851
= 7 + 851/2
= 858/2 = 429
Thus, the average of the odd numbers from 7 to 851 = 429 Answer
Method (2) to find the average of the odd numbers from 7 to 851
Finding the average of given continuous odd numbers after finding their sum
The odd numbers from 7 to 851 are
7, 9, 11, . . . . 851
The odd numbers from 7 to 851 form an Arithmetic Series in which
The First Term (a) = 7
The Common Difference (d) = 2
And the last term (ℓ) = 851
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 851
851 = 7 + (n – 1) × 2
⇒ 851 = 7 + 2 n – 2
⇒ 851 = 7 – 2 + 2 n
⇒ 851 = 5 + 2 n
After transposing 5 to LHS
⇒ 851 – 5 = 2 n
⇒ 846 = 2 n
After rearranging the above expression
⇒ 2 n = 846
After transposing 2 to RHS
⇒ n = 846/2
⇒ n = 423
Thus, the number of terms of odd numbers from 7 to 851 = 423
This means 851 is the 423th term.
Finding the sum of the given odd numbers from 7 to 851
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 851
= 423/2 (7 + 851)
= 423/2 × 858
= 423 × 858/2
= 362934/2 = 181467
Thus, the sum of all terms of the given odd numbers from 7 to 851 = 181467
And, the total number of terms = 423
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 851
= 181467/423 = 429
Thus, the average of the given odd numbers from 7 to 851 = 429 Answer
Similar Questions
(1) Find the average of the first 4170 even numbers.
(2) What is the average of the first 938 even numbers?
(3) Find the average of odd numbers from 7 to 1039
(4) Find the average of the first 4876 even numbers.
(5) Find the average of even numbers from 12 to 818
(6) Find the average of the first 4205 even numbers.
(7) Find the average of odd numbers from 7 to 773
(8) Find the average of the first 4589 even numbers.
(9) Find the average of the first 3905 odd numbers.
(10) Find the average of the first 1533 odd numbers.