Question

find the sum of all two digit odd multiples of 3​

Answer 1

Answer:

Step-by-step explanation:

2 digit odd multiples of 3

15,21,27......99

Find number of terms

I.e is a+(n-1)d

We know common difference=a2-a1

=21-15=6

So d=6

99=15+(n-1)6

84=(n-1)6

14=n-1

N=15

So apply= n/2(a+l)

= 15/2(15+99)

=15/2(114)

=15(57)

=855.

Hence proved.