42
Find the average of first 21 multiples of 21?
- A231
- B241
- C21
- D11
Answer not set
Discussion 1
Log in or create a free account to reply and vote.
0
CCommunity
First 21 multiples of 21 are - 21, 42, 63 …. 441
⇒ Average of odd number of consecutive terms is always equal to the value of the middle term
⇒ If there are n number of consecutive terms,
⇒ Average = [(n + 1)/2]th term
⇒ Here n = 21
∴ Average = [(21 + 1)/2]th term = 11th term
⇒ 11th term will be 11th multiple of 21 = 21 × 11 = 231
⇒ Average of odd number of consecutive terms is always equal to the value of the middle term
⇒ If there are n number of consecutive terms,
⇒ Average = [(n + 1)/2]th term
⇒ Here n = 21
∴ Average = [(21 + 1)/2]th term = 11th term
⇒ 11th term will be 11th multiple of 21 = 21 × 11 = 231