Find the sum of all two digit odd positive numbers?
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we will consider arithmetic progressions
a1(first term)=11
an(last term)=99
common difference=(an-an-1)=2
now for n
an=a+(n-1)d
99=11+2n-2
2n=90
n=45
sum will be=
n/2(a1+an)
45/2(11+99)
45/2*110
45*55
2475
a1(first term)=11
an(last term)=99
common difference=(an-an-1)=2
now for n
an=a+(n-1)d
99=11+2n-2
2n=90
n=45
sum will be=
n/2(a1+an)
45/2(11+99)
45/2*110
45*55
2475
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