AFCAT Model Paper 4

Given:
The average of certain first natural numbers is 10.5
Formula used:
Average = Sum of observations/ number of observations
Average of ‘first’ “n” natural numbers =

[n+1]

2

Calculation:
Average of certain first natural numbers =10.5=

[n+1]

2

⇒ n + 1 = 21
⇒ n = 20
Now, Sum of these first 20 natural numbers = average × 20
⇒ 10.5 × 20 = 210
∴ The sum of these numbers is 210.