Tips & Tricks Given: Average of certain first natural numbers is 20.5 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 =20.5=
[n+1]
2
⇒ n+1=41 ⇒ n=40 ∴ Sum of these first 40 natural numbers = average × number of observations =20.5×40=820