The positive integers are 1,3,5,7,9,..........
So the first term `a_1` is 1 and common difference d is 2 and number of terms n is 100.
`S_n=n/2(a_1+a_n)`
where `S_n` is the sum of the n terms of the arithmetic sequence and `a_n` is the nth term.
`S_n=n/2(a_1+a_1+(n-1)d)`
`S_n=n/2(2a_1+(n-1)d)`
Now plug in the values of `a_1` ,d and n
`S_100=100/2(2*1+(100-1)2)`
`S_100=50(2+99*2)`
`S_100=50*100*2`
`S_100=10000`
So, the sum of the first 100 positive odd integers is 10000
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