How to use the chart: two quick examples
A perfect square is a whole number times itself, like 9 = 3 × 3. A perfect cube is a whole number times itself three times, like 8 = 2 × 2 × 2.
A square patio covers 196 square feet. How long is each side?
The working
- The area of a square is side × side, so you need the number that squares to 196.
- Find 196 in the Square column. It’s on the row for 14.
- So √196 = 14, and each side is 14 feet.
Answer: 14 feet
A storage box is a cube, 5 feet on each side. How much does it hold?
The working
- The volume of a cube is side × side × side, which is 5³.
- Find 5 in the Number column and read the Cube column: 125.
Answer: 125 cubic feet
Estimate any square root without a calculator
Most numbers aren’t perfect squares. You can still get close without a calculator.
- Find the perfect squares on each side. 50 sits between 49 (7²) and 64 (8²).
- So √50 is between 7 and 8.
- 50 is much closer to 49, so √50 is just over 7. (It’s about 7.07.)
That’s often enough to pick the right answer choice, or to catch a calculator slip. The square root column does the same for 1 to 30, rounded to the hundredth.
3 mistakes that cost points
Mistake 1: squaring means doubling
9² is 9 × 9 = 81. It isn’t 9 × 2 = 18. The little 2 says how many 9s to multiply.
Mistake 2: a negative number on the calculator
On the GED calculator, typing −5 and then x² gives −25. The calculator squares the 5 first. Type (−5)² with the parentheses to get 25.
Mistake 3: splitting a square root over a plus sign
√(9 + 16) is √25 = 5. Taking √9 + √16 = 3 + 4 = 7 is wrong. Add first, then take the root. This one shows up in the Pythagorean theorem.
Keep going
Exponents and roots practice
Exponent rules, square and cube roots and scientific notation, with the working shown.
Volume of a cylinder
Square the radius, then multiply: worked examples and five practice questions.
Math formula sheet
Every GED-level formula with a worked example, including the Pythagorean theorem.
Fraction to decimal chart
Every fraction from 1/2 to 1/64 with its exact decimal, on one page.
Written by
Coach Crissy
Math instructor
Coach Crissy teaches the video lessons behind the BooknBoost GED math course, working through GED-style problems on camera: ratios and proportions, percent and interest, mean, median and mode, slope, and the geometry students meet on test day.