Question

Ex. 6. Find the average of first 20 multiples of 7.
7 (1+2+3+ ... +20)
Sol. Required average = -
20

Answer 1

Answer:

Step-by-step explanation:

sum of n natural numbers is [n(n+1)]/2

so 7(1+2+3..........+20)

= 7[{20(20+1)}/2]

7[10(21)]

70*21

average =70*21/20

=147/2

=73.5