Question

find the sum of all 6 digit numbers which are divisible by 7

Answer 1

Answer:

147

Step-by-step explanation:

sum of first 6 digits of numbers divisible by 7 are

7+14+21+28+35+42

=147

Answer 2

Answer:

Thus thesum of all 6 digit numbers which are divisible by 7

=70,714,664,286

Step-by-step explanation:

6 digit numbers are

from 100000 to 999999

we can write these numbers as:

100000=14285*7+5

Adding 2 both sides

100002=14285*7+7=1486*7

So first 6 digit no divisible by 7 is say a= 100002

Now 999999 =142857*7+0

Thus l= 999999 is the biggest 6 digit no divisible by 7

thus all such no are:

100002,100009,100016,100023.....................................999999

This is an AP with a=100002 l=999999 d=7 then n=?

We know that

l = a+(n-1)*d

999999=100002+(n-1)*7

(n-1)*7=999999-100002=899997

n-1 =899997/7=128571

n=128572

Thus sum =n/2( a+l)

=128572/2*( 100002+999999)

=64286 x 1100001

=70714664286