Also, theoretically

.9 x 100 = 90.0 grams

1 x 100 = 100 grams

So simply by lifting each bag by hand you would notice a 10 gram difference.

2 coins from the 2nd roll

3 coins from the 3rd roll…………..

……..10 coins from the 4th roll

there will be 55 and weigh them together.

let us take for eg that the .9 coins are in the 4th roll.if we weigh the 55 coins the total weight would be-

1 x 1=1

2 x 1=2

3 x 1=3

4 x .9=3.6

5 x 1=5

6 x 1=6

7 x 1=7

8 x 1=8

9 x 1=9

10 x 1=10

total ans is 54.6.sub tract that from 55 the ans is .4 hence the .9g coins are in the 4th roll.

the tens place decide the roll