move the decimal 2 spaces to the right. 2.16-->216 You need 21 ten rods and 6 cubes...... I wouldn't do 2 hundred flats because 2 isn't divisible by 3. Put the ten rods into 3 equal group, then do the same with the cubes. You should end up with 7 in each group since 21 divided by 3 is 7. You should also end up with 2 cubes in each group. So in one group you have 72. Now move the decimal back to where it came from, 2 spaces to the left. Now you have 0.72.