Home › CBSE Class 9 › mathematics › c9sumnaturals › Per NCERT Class 9 Math, what is the FORMULA for …
Per NCERT Class 9 Math, what is the FORMULA for the sum of the first n natural numbers?
ASₙ = (n + 1)² / 2
BSₙ = n(n + 1) / 2
CSₙ = n²
DSₙ = n(n − 1) / 2
Answer & Solution
Correct answer: B. Sₙ = n(n + 1) / 2
Per NCERT §8.5, Sₙ = 1 + 2 + ... + n = n(n+1)/2. The other formulas misstate.
Related questions
Per NCERT, what is the sum of the first 20 natural numbers (1 + 2 + ... + 20)?Per NCERT, the sum of 2-digit numbers DIVISIBLE BY 3 (12, 15, 18, ..., 99) is which value?Per NCERT, a child arranges marbles in rows: 1 marble in row 1, 2 in row 2, 3 in row 3, ..Per NCERT, the second part of Aryabhata's verse describes Sₙ as which equivalent expressioPer NCERT, the proof of Sₙ = n(n+1)/2 uses the algebraic identity 2S = n(n+1). What is thePer NCERT, the sum 25 + 26 + 27 + ... + 58 can be computed as which expression?Per NCERT, what is the 10th triangular number using tₙ = n(n+1)/2?Per NCERT, the nth TRIANGULAR NUMBER tₙ (1, 3, 6, 10, 15, ...) equals the sum of the first