Add to 100

Algebra Level 1

Without using a calculator, what is 1+2+3+4+5+6+7+8+9+10+11+12+13+14…+99+100


The answer is 5050.

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3 solutions

Hana Wehbi
Dec 2, 2018

∑ 1 n = 100 k = n ( n + 1 ) 2 = 100 × 101 2 = 5050 \sum_{1}^{n=100} k =\frac{n(n+1)}{2}=\frac{100\times101}{2}=5050

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S = 100 ( 100 + 1 ) 2 = 100 ( 101 ) 2 = 5050 S = \dfrac {100(100+1)}{2} = \dfrac {100(101)}{2} = \boxed{5050}

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I think you mean 100 ( 101 ) 2 \frac {100(101)}{2}

Parth Sankhe - 2 years, 6 months ago

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Ops!!!..... Typing Error!!.... I didnt notice that!!..... Thanks

A Former Brilliant Member - 2 years, 6 months ago

The answer is 5050

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