which is greater 1.2, 1.23, or 1.1?

Line them up by their decimal points:
1.1
1.2
1.23

If it helps, pad the end with zeroes to make them the same length:
1.10
1.20
1.23

Now you can compare them by looking at their digits going left to right.
1.2 > 1.1

And:
1.23 > 1.2

Answer:
1.23 is the greatest

1.23 is the greatest, then 1.2 and then 1.1.

You can think of it in the sense that they are 1.23, 1.20, 1.10 respectively, hence 1.2 is always greater than 1.1, and then 3 is greater than 0 which shows that:

1.23>1.20>1.10

1.23
(1.23>1.2>1.1)
REASON AND PROOF:
* subtract each number by a number already given, we get,
proof 1:
subtract with a number that u think is the smallest(say, 0.1)
1.2 - 1.1 ; 1.23 - 1.1 ; 1.1 - 1.1
so, we are left with,
0.1 ; 0.12 ; 0
this tells that,
1.1 was the smallest value as you obtain 0 on subtracting with itself and u get a positive quantity for other arguments.
Now, you must compare 0.1 and 0.12...
by subtracting 0.1, we get,
0.1 - 0.1 ; 0.12 - 0.1
or,
0 ; 0.02
here, 0.1 is smaller than 0.12.
Now, as we have said that 0.1 is smallest and 0.1 is smaller than 0.12, we get,
1.23>1.2>1.1

logic: a-b will yield a positive answer if a>b, and, the same will yield a negative answer if b>a

proof 2:
now, subtract all numbers from a number already given and that which u think is the greatest...
the logic here is, if it is the greatest number, the answer which u get must be -ve... and subtracting by itself will give 0
so,
try subtracting by 1.2... we get
0 ; 0.03 ; -1
This indicates, 1.2>1.1 ... but is lesse than 1.23.
if u try doing the same from 1.23,
we get,
-0.03 ; 0 ; -0.13

thus, 1.23 is the greatest.

1.23 is the greatest number out of the three. You're basically asking: which is greater, 120, 123 or 110.

1.23 is grater than all given no..
according to descending order 1.23 >1.2 >1.1

1.23 is greater than 1.2 or 1.1

1.23 is greater than 1.2 and 1.1

1.2=12/10, 1.23=123/100, 1.1=11/10

1.2=120/100, 1.23=123/100, 1.1=110/100 so 1.23 is greater

1.2= (1200)/1000 = 1000+200
1.23=(1230)/1000=1000+230
1.1=(1100)/1000 =1000+100
so it is clear that, 1.23 > 1.2 > 1.1

1.23 is greater than 1.2 or 1.1