Question

Without adding find the sum 1+3+5+7................+23​

Answer 1

Answer:

276

Explanation:

Sum of n numbers = $\frac{n(n+1)}{2}$ = $\frac{23*24}{2}$ = 276

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Answer 2

a=1

d=3-1=2.

l=23.

A(n)=a+(n-1)d.

=>23=1+(n-1)2.

=>23-1=(n-1)2.

=>22/2=n-1.

=>11=n-1.

=>n=11+1=12.

S(n)=n/2(a+l)

S(12)=12/2(1+23).

S(12)=6*24.

=>S(12)=144.

The sum is 144.