To find the length of the side marked with a question mark, we can use the Pythagorean theorem. This theorem applies to right-angled triangles (triangles with one 90-degree corner).
Step 1: Identify the sides
* The two shorter sides (legs) are given as
20 cm and
21 cm.
* The longest side opposite the right angle is called the hypotenuse. This is the side marked with the
?. Let's call this length $c$.
Step 2: Use the formula
The Pythagorean theorem states:
$$a^2 + b^2 = c^2$$
Where:
* $a$ and $b$ are the lengths of the shorter sides.
* $c$ is the length of the hypotenuse.
Step 3: Plug in the numbers
$$20^2 + 21^2 = c^2$$
Step 4: Calculate the squares
* $20 \times 20 = 400$
* $21 \times 21 = 441$
So, the equation becomes:
$$400 + 441 = c^2$$
Step 5: Add the numbers together
$$841 = c^2$$
Step 6: Find the square root
To find $c$, we need to find the number that, when multiplied by itself, equals 841.
$$\sqrt{841} = 29$$
(Check: $29 \times 29 = 841$)
So, the length of the missing side is 29 cm.
Final Answer:
29 cm
Parent Tip: Review the logic above to help your child master the concept of pythagorean theorem math problems.
