Question

Find the sum of all 3's that are needed to write the number from 200 to 400

Answer 1

There will be 10 numbers from 200 to 299 that will end with 3 ( 203, 213, 223........ 293 ).
There will be 100 numbers from 300 to 400 that will begin with 3, we will not count the numbers that will end with because they will be repeated.
Total numbers = 10 + 100 = 110

Answer 2

Answer:

The sum is 420.

Step-by-step explanation:

Given: Numbers from 200 to 400.

To find: Sum of all 3's.

First consider numbers from 200 to 299.

In this range in unit place we have 10 3's & in tens place i.e; $230,.....,239$ total 10 3's.

There is no 3 in hundred place.

Now consider numbers from 300 to 400.

Here in unit place 3's are 10, in tens place 3's are 10 and on hundred place 100 3's are there as whole range is of 300.

So, total 3's from 200-400$=10+10+10+10+100=140$.

Therefore the sum of all 3's is $=3*140=420$.

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