Question

What is the sum of 1 +2 +3 +... +98 +99 +100

Answer 1

Answer:

5050

Step-by-step explanation:

100(100+1)/2

=50(101)

=5050

Answer 2

Answer:5050

Step-by-step explanation:

an=a+(n-1)d

100=1+(n-1)1 [common difference=1]

99=n-1

n=100

Sn=n/2[2a+(n-1)d]

sn=100/2[2(1)+(100-1)1]

sn=50[2+99]

sn=50[101]

5050

Or

Sn=n/2[a+an]

Sn=100/2[1+101]

Sn=50[101]

Sn=5050

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