Question

Find the sun of ap 1 3 5 7 + ...... + 99

Answer 1

$\texttt{Answer :}$

The series of AP is

1 + 3 + 5 + 7 + . . . + 99

1st term = 1 and common difference = 2

Let, nth term is 99

Then,

1 + (n - 1) × (2) = 99

or, 1 + 2n - 2 = 99

or, 2n - 1 = 99

or, 2n = 100

or, n = 50

So, the AP series has 50 terms.

Hence, sum of the serial is

= 50/2 × (1st term + last term)

= 25 × (1 + 99)

= 25 × 100

= $\fbox{2500}$

#$\textbf{MarkAsBrainliest}$

Answer 2

first term = 1
difference =2
l=a+n-1 ×d
99=1+n-1×2
98=2n-2
98+2=2n
100=2n
n=100÷2
n=50
then no of terms =50
sn =n÷2{2a+(n-1)d}
sn =50÷2× 100
sn=25×100
sn=2500