Each step left of the decimal is tens, hundreds, and so on. Each step right is tenths, hundredths, and thousandths. ACT Math uses that to hide a simple comparison inside a long decimal. Fractions of the same values are in fractions and ratios.
Line up the decimal
0.5 is five tenths, which is 1/2. 0.05 is five hundredths, which is 1/20. They are not close. When you add or subtract, line up the decimal points, not the rightmost digit. 1.2 + 0.35 is 1.55, not 1.37 and not 4.7.
Multiplying by 10 moves the decimal one place right. Dividing by 10 moves it one place left. Scientific notation is that shift written with a power of 10, in scientific notation.
Percent is a decimal move
8% is 0.08, not 0.8. The percent questions that use that conversion are in percent problems. Place-value traps inside a larger word problem are in setting up word problems.
The bottom line
Name the place before you compare. A zero between the decimal and the digit makes the number smaller, not decorative.
Start practicing
Start with a free diagnostic, then drill your weak spots with 15-question quizzes and track how you're doing across Reading, English, and Math. Compare plans whenever you're ready to go further.
This article offers general ACT prep guidance. The ACT can change from year to year, including its format, scoring, policies, test dates, and fees, so always confirm the latest details on the official ACT website at act.org before you make decisions. ACT® is a registered trademark of ACT, Inc. thirty-six is not affiliated with, endorsed by, or sponsored by ACT.