alleryThe sum of the first n natural numbers is:
An(n+1)/3
Bn(n+2)/2
Cn(n+1)/2
Dn(n-1)/2
Answer & Solution
Correct answer: C. n(n+1)/2
1. Write the sum forwards and then backwards.
2. Adding the two lines pairs every term to give n plus 1.
3. That gives the formula n(n+1)/2.
4. So the answer is n(n+1)/2.
_Source: syllabus Mathematics, Ch 8 'Predicting What Comes Next: Exploring Sequences and Progressions'_
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