Question:
Find the average of the first 3520 odd numbers.
Correct Answer
3520
Solution And Explanation
Explanation
Method to find the average
Step : (1) Find the sum of given numbers
Step: (2) Divide the sum of given number by the number of numbers. This will give the average of given numbers
The first 3520 odd numbers are
1, 3, 5, 7, 9, . . . . 3520 th terms
Calculation of the sum of the first 3520 odd numbers
We can find the sum of the first 3520 odd numbers by simply adding them, but this is a bit difficult. And if the list is long, it is very difficult to find their sum. So, in such a situation, we will use a formula to find the sum of given numbers that form a particular pattern.
Here, the list of the first 3520 odd numbers forms an Arithmetic series
In an Arithmetic Series, the common difference is the same. This means the difference between two consecutive terms are same in an Arithmetic Series.
The sum of n terms of an Arithmetic Series
Sn = n/2 [2a + (n – 1) d]
Where, n = number of terms, a = first term, and d = common difference
In the series of first 3520 odd number,
n = 3520, a = 1, and d = 2
Thus, sum of the first 3520 odd numbers
S3520 = 3520/2 [2 × 1 + (3520 – 1) 2]
= 3520/2 [2 + 3519 × 2]
= 3520/2 [2 + 7038]
= 3520/2 × 7040
= 3520/2 × 7040 3520
= 3520 × 3520 = 12390400
⇒ The sum of first 3520 odd numbers (Sn) = 12390400
Shortcut Method to find the sum of first n odd numbers
Thus, the sum of first n odd numbers = n2
Thus, the sum of first 3520 odd numbers
= 35202 = 12390400
⇒ The sum of first 3520 odd numbers = 12390400
Calculation of the Average of the first 3520 odd numbers
Formula to find the Average
Average = Sum of given numbers/Number of numbers
Thus, The average of the first 3520 odd numbers
= Sum of first 3520 odd numbers/3520
= 12390400/3520 = 3520
Thus, the average of the first 3520 odd numbers = 3520 Answer
Shortcut Trick to find the Average of the first n odd numbers
The average of the first 2 odd numbers
= 1 + 3/2
= 4/2 = 2
Thus, the average of the first 2 odd numbers = 2
The average of the first 3 odd numbers
= 1 + 3 + 5/3
= 9/3 = 3
Thus, the average of the first 3 odd numbers = 3
The average of the first 4 odd numbers
= 1 + 3 + 5 + 7/4
= 16/4 = 4
Thus, the average of the first 4 odd numbers = 4
The average of the first 5 odd numbers
= 1 + 3 + 5 + 7 + 9/5
= 25/5 = 5
Thus, the average of the first 5 odd numbers = 5
Thus, the Average of the the First n odd numbers = n
Thus, the average of the first 3520 odd numbers = 3520
Thus, the average of the first 3520 odd numbers = 3520 Answer
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