Question

21. Find the sum of all two digit numbers divisible by 3 ?​

Answer 1

Answer:

1665

Step-by-step explanation:

First two digit number divisible by 3 = 12

last two digit numbers divisible by 3 = 99

S30 = 15 × 111 = 1665

Answer 2

Step-by-step explanation:

hello!! here is the detail explanation..

The first two digit number which is divisible by 3 is 12

So let's consider the first term of the arithmetic progression as 12.

The last two digit number which is divisible by 3 is 99

So let's consider the last term of the arithmetic as 99.

so, a=12

d=3

l=99

a+(n-1)d=99

substituting the values we get,

12+(n-1)*3=99

12+3n-3=99

9+3n=99

3n=99-9

3n=90

n=90÷3

n=30

So there are 30 terms in total

So the sum is:-

(30÷2)(12+99)

15(12+99)

15(111)

1665

So the sum of all 2 digits number divisible by 3 is 1665.

Hope this helped you!!