Question

what is the sum of first 25 terms of an arethamatic sequence 1,3,5.....?​

Answer 1

Answer:

625

Step-by-step explanation:

Sequence: 1, 3, 5...

First term (a) = 1

Number of terms to be added (n) = 25

Common difference (d) = a2 - a1 = 3 -1 = 2

Sum of first 25 terms

$= \frac{n}{2}(2a+(n-1)d)\\ \\= \frac{25}{2}(2(1)+(25-1)2)\\ \\=12.5(2+(24)2)\\\\=12.5(2+48)\\\\=12.5(50)\\\\=12.5*50\\\\=125*5\\\\=625$

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Answer 2

Step-by-step explanation:

A=1 , D=2 , {N=25

= N/2 (2a+(n−1)d)

25/2{2*1+(25-1)*2}

25/2{2+(24*2)}

25/2{2+48}

25/2(50)

=25*25

=625....