Question

what is the sum of all 2 digit odd numbers

Answer 1

Here is your answer ☺
Dear,,,, @User...

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✴Two digit odd positive numbers are 11,13,15,17...........99 are in A.P. (As possible)
✴Here a = 11
and
d = 2, tn= 99,
n = ?

⭐∴sum of all two digit odd positive numbers = 2475.....
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Answer 2

a1=11
d=2
an=99
n=?
Sn =?
an=a+(n-1)d
99=11+(n-1)2
88/2=n-1
44=n-1
45=n
n=45
Sn=n/2(a+l)
S45=45/2(11+99)
S45=45/2×110
S45=4950/2
S45=2475