Question:
What is the average of the first 760 even numbers?
Correct Answer
761
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 the given numbers
The first 760 even numbers are
2, 4, 6, 8, . . . . 760 th terms
Calculation of the sum of the first 760 even numbers
We can find the sum of the first 760 even 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 760 even 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 the first 760 even number,
n = 760, a = 2, and d = 2
Thus, sum of the first 760 even numbers
S760 = 760/2 [2 × 2 + (760 – 1) 2]
= 760/2 [4 + 759 × 2]
= 760/2 [4 + 1518]
= 760/2 × 1522
= 760/2 × 1522 761
= 760 × 761 = 578360
⇒ The sum of the first 760 even numbers (S760) = 578360
Shortcut Method to find the sum of the first n even numbers
Thus, the sum of the first n even numbers = n2 + n
Thus, the sum of the first 760 even numbers
= 7602 + 760
= 577600 + 760 = 578360
⇒ The sum of the first 760 even numbers = 578360
Calculation of the Average of the first 760 even numbers
Formula to find the Average
Average = Sum of the given numbers/Number of the numbers
Thus, The average of the first 760 even numbers
= Sum of the first 760 even numbers/760
= 578360/760 = 761
Thus, the average of the first 760 even numbers = 761 Answer
Shortcut Trick to find the Average of the first n even numbers
(1) The average of the first 2 even numbers
= 2 + 4/2
= 6/2 = 3
Thus, the average of the first 2 even numbers = 3
(2) The average of the first 3 even numbers
= 2 + 4 + 6/3
= 12/3 = 4
Thus, the average of the first 3 even numbers = 4
(3) The average of the first 4 even numbers
= 2 + 4 + 6 + 8/4
= 20/4 = 5
Thus, the average of the first 4 even numbers = 5
(4) The average of the first 5 even numbers
= 2 + 4 + 6 + 8 + 10/5
= 30/5 = 6
Thus, the average of the first 5 even numbers = 6
Thus, the Average of the First n even numbers = n + 1
Thus, the average of the first 760 even numbers = 760 + 1 = 761
Thus, the average of the first 760 even numbers = 761 Answer
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