Question : Find the average of odd numbers from 13 to 1489
Correct Answer 751
Solution & Explanation
Solution
Method (1) to find the average of the odd numbers from 13 to 1489
Shortcut Trick to find the average of the given continuous odd numbers
The odd numbers from 13 to 1489 are
13, 15, 17, . . . . 1489
After observing the above list of the odd numbers from 13 to 1489 we find that the difference between two consecutive terms are equal. This means the list of the odd numbers from 13 to 1489 form an Arithmetic Series.
In the Arithmetic Series of the odd numbers from 13 to 1489
The First Term (a) = 13
The Common Difference (d) = 2
And the last term (ℓ) = 1489
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 13 to 1489
= 13 + 1489/2
= 1502/2 = 751
Thus, the average of the odd numbers from 13 to 1489 = 751 Answer
Method (2) to find the average of the odd numbers from 13 to 1489
Finding the average of given continuous odd numbers after finding their sum
The odd numbers from 13 to 1489 are
13, 15, 17, . . . . 1489
The odd numbers from 13 to 1489 form an Arithmetic Series in which
The First Term (a) = 13
The Common Difference (d) = 2
And the last term (ℓ) = 1489
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 13 to 1489
1489 = 13 + (n – 1) × 2
⇒ 1489 = 13 + 2 n – 2
⇒ 1489 = 13 – 2 + 2 n
⇒ 1489 = 11 + 2 n
After transposing 11 to LHS
⇒ 1489 – 11 = 2 n
⇒ 1478 = 2 n
After rearranging the above expression
⇒ 2 n = 1478
After transposing 2 to RHS
⇒ n = 1478/2
⇒ n = 739
Thus, the number of terms of odd numbers from 13 to 1489 = 739
This means 1489 is the 739th term.
Finding the sum of the given odd numbers from 13 to 1489
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 13 to 1489
= 739/2 (13 + 1489)
= 739/2 × 1502
= 739 × 1502/2
= 1109978/2 = 554989
Thus, the sum of all terms of the given odd numbers from 13 to 1489 = 554989
And, the total number of terms = 739
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 13 to 1489
= 554989/739 = 751
Thus, the average of the given odd numbers from 13 to 1489 = 751 Answer
Similar Questions
(1) Find the average of the first 4439 even numbers.
(2) What will be the average of the first 4222 odd numbers?
(3) What will be the average of the first 4355 odd numbers?
(4) What will be the average of the first 4161 odd numbers?
(5) Find the average of even numbers from 10 to 1860
(6) Find the average of the first 3980 even numbers.
(7) Find the average of odd numbers from 15 to 217
(8) Find the average of the first 3081 odd numbers.
(9) Find the average of odd numbers from 15 to 757
(10) Find the average of even numbers from 4 to 630