Write these masses in order, starting with the lightest. 1.25 kilograms, 0.99 kilograms, 1.025 kilograms, and 0.009 kilograms.
We need to compare these four different masses to find the lightest. If we look at the ones digit, we can see that two of the masses are less than one kilogram. 0.99 has no ones, and 0.009 has no ones either. Both of these masses are less than one kilogram.
Because both of these masses have a zero in the ones place, we need to move to the next digit to the right and compare the tenths digit. 0.99 has nine-tenths and 0.009 has no tenths. So 0.009 is the lightest. And we can write 0.99 as the next lightest because we know it’s less than one kilogram.
Now what we have to do is compare 1.25 and 1.025. 1.25 has a two in the tenth column. And 1.025 has no tenths. So the smallest of these two masses is 1.025. This means that 1.25 is the heaviest. So the masses in order, starting with the lightest are: 0.009 kilograms, 0.99 kilograms, 1.025 kilograms, and 1.25 kilograms.