Find a missing side of a right triangle
Grade 8 Math Worksheet - Building Confidence

Circle the best answer, or write your answer on the line.
Ari cuts a right triangle from card paper for an art project. How long is the hypotenuse, in inches?
Bo's drawing robot draws a right triangle and then beeps very proudly. How long is the hypotenuse, in cm?
Right triangle, right-angle mark at the bottom-right corner. Legs 6 cm and 8 cm; the hypotenuse, across from the mark, is marked ?. Not to scale. Strip under it: 6 × 6 = ?, 8 × 8 = ?, add the two squares = ?, then ? × ? = that sum, the same whole number in both boxes. Right triangle, right-angle mark at the bottom-right corner. Legs 6 cm and 8 cm; the hypotenuse, across from the mark, is marked ?. Not to scale. Strip under it: 6 × 6 = ?, 8 × 8 = ?, add the two squares = ?, then ? × ? = that sum, the same whole number in both boxes. 6 cm 8 cm ? Not to scale Esme's class marks out a right-triangle flower bed with string. How long is the hypotenuse, in feet?
Right triangle, right-angle mark at the top-left corner. Legs 21 feet and 28 feet; the hypotenuse, across from the mark, is marked ?. Not to scale. Strip under it: 21 × 21 = ?, 28 × 28 = ?, add the two squares = ?, then ? × ? = that sum, the same whole number in both boxes. Right triangle, right-angle mark at the top-left corner. Legs 21 feet and 28 feet; the hypotenuse, across from the mark, is marked ?. Not to scale. Strip under it: 21 × 21 = ?, 28 × 28 = ?, add the two squares = ?, then ? × ? = that sum, the same whole number in both boxes. 21 feet 28 feet ? Not to scale Jun sews a right-triangle quilt patch. How long is the hypotenuse of the patch, in inches?
Right triangle, right-angle mark at the top-right corner. Legs 5 inches and 12 inches; the hypotenuse, across from the mark, is marked ?. Not to scale. Strip under it: 5 × 5 = ?, 12 × 12 = ?, add the two squares = ?, then ? × ? = that sum, the same whole number in both boxes. Right triangle, right-angle mark at the top-right corner. Legs 5 inches and 12 inches; the hypotenuse, across from the mark, is marked ?. Not to scale. Strip under it: 5 × 5 = ?, 12 × 12 = ?, add the two squares = ?, then ? × ? = that sum, the same whole number in both boxes. 5 inches 12 inches ? Not to scale Kira draws a right triangle on poster paper but forgets to label one leg. How long is that leg, in feet?
Right triangle, right-angle mark at the bottom-left corner. The hypotenuse, across from the mark, is 10 feet. One leg is 6 feet; the other leg is marked ?. Not to scale. Strip under it: 10 × 10 = ?, 6 × 6 = ?, take the small square off the big one = ?, then ? × ? = that area, the same whole number in both boxes. Right triangle, right-angle mark at the bottom-left corner. The hypotenuse, across from the mark, is 10 feet. One leg is 6 feet; the other leg is marked ?. Not to scale. Strip under it: 10 × 10 = ?, 6 × 6 = ?, take the small square off the big one = ?, then ? × ? = that area, the same whole number in both boxes. 10 feet 6 feet ? Not to scale Luz cuts a right triangle out of felt. The scissors are extra sharp today. How long is the unlabeled leg, in inches?
Right triangle, right-angle mark at the bottom-right corner. The hypotenuse, across from the mark, is 13 inches. One leg is 5 inches; the other leg is marked ?. Not to scale. Strip under it: 13 × 13 = ?, 5 × 5 = ?, take the small square off the big one = ?, then ? × ? = that area, the same whole number in both boxes. Right triangle, right-angle mark at the bottom-right corner. The hypotenuse, across from the mark, is 13 inches. One leg is 5 inches; the other leg is marked ?. Not to scale. Strip under it: 13 × 13 = ?, 5 × 5 = ?, take the small square off the big one = ?, then ? × ? = that area, the same whole number in both boxes. 13 inches 5 inches ? Not to scale Milo's math book shows a right triangle with one leg missing its label. How long is that leg, in cm?
Right triangle, right-angle mark at the top corner. The hypotenuse, across from the mark, is 17 cm. One leg is 15 cm; the other leg is marked ?. Not to scale. Strip under it: 17 × 17 = ?, 15 × 15 = ?, take the small square off the big one = ?, then ? × ? = that area, the same whole number in both boxes. Right triangle, right-angle mark at the top corner. The hypotenuse, across from the mark, is 17 cm. One leg is 15 cm; the other leg is marked ?. Not to scale. Strip under it: 17 × 17 = ?, 15 × 15 = ?, take the small square off the big one = ?, then ? × ? = that area, the same whole number in both boxes. 17 cm 15 cm ? Not to scale Noah draws a long, thin right triangle with a crayon. How long is the unlabeled leg, in cm?
Right triangle, right-angle mark at the top-left corner. The hypotenuse, across from the mark, is 25 cm. One leg is 24 cm; the other leg is marked ?. Not to scale. Strip under it: 25 × 25 = ?, 24 × 24 = ?, take the small square off the big one = ?, then ? × ? = that area, the same whole number in both boxes. Right triangle, right-angle mark at the top-left corner. The hypotenuse, across from the mark, is 25 cm. One leg is 24 cm; the other leg is marked ?. Not to scale. Strip under it: 25 × 25 = ?, 24 × 24 = ?, take the small square off the big one = ?, then ? × ? = that area, the same whole number in both boxes. 25 cm 24 cm ? Not to scale Pia lays a right triangle of foam tiles on the gym floor. How long is the unlabeled leg, in inches?
Right triangle, right-angle mark at the bottom-left corner. The hypotenuse, across from the mark, is 20 inches. One leg is 16 inches; the other leg is marked ?. Not to scale. Strip under it: 20 × 20 = ?, 16 × 16 = ?, take the small square off the big one = ?, then ? × ? = that area, the same whole number in both boxes. Right triangle, right-angle mark at the bottom-left corner. The hypotenuse, across from the mark, is 20 inches. One leg is 16 inches; the other leg is marked ?. Not to scale. Strip under it: 20 × 20 = ?, 16 × 16 = ?, take the small square off the big one = ?, then ? × ? = that area, the same whole number in both boxes. 20 inches 16 inches ? Not to scale Ren must find the hypotenuse of a right triangle drawn on paper. Which first step is right?
Right triangle, right-angle mark at the bottom-left corner. Legs 15 cm and 36 cm; the hypotenuse is marked ?. Not to scale. Right triangle, right-angle mark at the bottom-left corner. Legs 15 cm and 36 cm; the hypotenuse is marked ?. Not to scale. 15 cm 36 cm ? Not to scale - Add the sides: 15 + 36
- Add the squares: 15² + 36²
- Subtract the squares: 36² − 15²