Question

Find the sum of all two digit odd multiples of 3.
plz answer this question
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Answer 1

Since,

First two digit odd multiple of 3 = 15

a=15

d=6

l=99

n=?

l=a+(n-1)d

99=15+(n-1)6

99-15=6n-6

84+6=6n

$\frac{90}{6} = n$

n=15

$s_{n} = \frac{n}{2} \times (2a + (n - 1)d)$

=15/2(30+84)

=15/2(114)

=15*57

=855