Pascal and Current Year

The given picture represents the Pascal triangle. What is the sum of the numbers in the 2018th row?

2 2020 2^{2020} 2 2018 2^{2018} 2 2017 2^{2017} 2 2016 2^{2016} 2 2021 2^{2021}

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2 solutions

Chew-Seong Cheong
Nov 11, 2018

Relevant wiki: Binomial Theorem

By binomial theorem, we have ( 1 + x ) n = k = 0 n ( n k ) x k \displaystyle (1+x)^n = \sum_{k=0}^n \binom nk x^k . Putting x = 1 x=1 , k = 0 n ( n k ) = 2 n \displaystyle \implies \sum_{k=0}^n \binom nk = 2^n . That is the sum of numbers of the ( n + 1 ) (n+1) th row of Pascal triangle is equal to 2 n 2^n . Therefore, that for the 2018th row is 2 2017 \boxed{2^{2017}} .

Sir, something went wrong with your LaTeX.

X X - 2 years, 7 months ago

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Thanks, I have fixed it.

Chew-Seong Cheong - 2 years, 7 months ago

Thank you, nice solution.

Hana Wehbi - 2 years, 7 months ago
Hana Wehbi
Nov 11, 2018

Note that:

Row 1: sum of numbers is 2 1 1 = 2 0 = 1 2^{1-1}=2^0= 1

Row 2: sum of numbers is 2 2 1 = 2 1 = 2 2^{2-1}=2^1= 2

Row 3: sum of numbers is 2 3 1 = 2 2 = 4 2^{3-1}=2^2= 4

Row 4: sum of numbers is 2 4 1 = 2 3 = 8 2^{4-1}=2^3= 8

Thus, sum of numbers in the Row 2018 is : 2 2018 1 = 2 2017 2^{2018-1}= 2^{2017}

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