If you look at the tens place of the decimal-
.8 and .6
You will see that 8 is larger than 6.
Furthermore,
Look at it this way:
0 1 2 3 4 5 6 7 8
The farther the number is to zero, the larger in quantity it is.
And since the .6 and the .8 are in the same place, and the whole numbers are both 1, 1.87 is greater than 1.648.
I hope this helps!
~cupcake
