Perfect Squares and Square Roots Flashcards (1–20)
40 cards · free to study, print and copy
Perfect Squares and Square Roots Flashcards (1–20)
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About this deck
The first 20 cards ask for the square of each whole number from 1 to 20. The next 20 ask for the square root of each of those perfect squares, from √1 = 1 to √400 = 20.
Knowing squares up to 20² speeds up a lot of middle and high school math: simplifying radicals, using the Pythagorean theorem, factoring quadratics and estimating roots.
Study the two halves separately at first, then shuffle them together.
Study tips
- Squares of numbers ending in 5 follow a pattern: for 15², multiply 1 × 2 = 2 and attach 25 to get 225.
- Use neighbors: 14² = 13² + 13 + 14 = 169 + 27 = 196.
- Perfect squares never end in 2, 3, 7 or 8, which helps you spot non-squares quickly.
- Learn 1²–12² first (they overlap with the times table), then 13²–20².
All 40 cards
| Front | Back |
|---|---|
| 1² | 1 |
| 2² | 4 |
| 3² | 9 |
| 4² | 16 |
| 5² | 25 |
| 6² | 36 |
| 7² | 49 |
| 8² | 64 |
| 9² | 81 |
| 10² | 100 |
| 11² | 121 |
| 12² | 144 |
| 13² | 169 |
| 14² | 196 |
| 15² | 225 |
| 16² | 256 |
| 17² | 289 |
| 18² | 324 |
| 19² | 361 |
| 20² | 400 |
| √1 | 1 |
| √4 | 2 |
| √9 | 3 |
| √16 | 4 |
| √25 | 5 |
| √36 | 6 |
| √49 | 7 |
| √64 | 8 |
| √81 | 9 |
| √100 | 10 |
| √121 | 11 |
| √144 | 12 |
| √169 | 13 |
| √196 | 14 |
| √225 | 15 |
| √256 | 16 |
| √289 | 17 |
| √324 | 18 |
| √361 | 19 |
| √400 | 20 |
Frequently asked questions
›What is a perfect square?
A whole number that is the square of another whole number, such as 49 = 7².
›Isn't the square root of 49 also −7?
Both 7 and −7 square to 49, but the √ symbol means the principal (non-negative) root, so √49 = 7.
›Why stop at 20?
Squares up to 20² cover most of what comes up in school math and standardized tests. Beyond that, a calculator or estimation is usually fine.
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