How to Solve Pythagorean Theorem Problems? (+FREE Worksheet!)

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In mathematics, the Pythagorean Theorem is the relationship between three sides of a right triangle.

How to Solve Pythagorean Theorem Problems? (+FREE Worksheet!)
Tutor-style math help

Solve Pythagorean Theorem Problems: what to notice and how to work it

Geometry skill
Geometry topics become easier when the diagram is labeled before formulas appear. The picture tells you which measurements are lengths, areas, angles, or volumes.

What to notice first

Draw or inspect the figure first. Mark known values, name the unknown, and check whether the answer should use units, square units, or cubic units.

Common student mistake

Do not plug into a formula before checking what the question asks for. Area, perimeter, surface area, and volume use different measurements.

Key formulas and cues

\(d=\sqrt{(x_2-x_1)^2+(y_2-y_1)^2}\)
\(M=\left(\frac{x_1+x_2}{2},\frac{y_1+y_2}{2}\right)\)
\(A=lw\)
\(V=lwh\)
lengthwidth baseheight label the picture first

A reliable path

  1. Label the diagramWrite each given measurement on the figure.
  2. Choose the formulaMatch the formula to distance, midpoint, area, volume, or angle relationships.
  3. Check unitsUse linear, square, or cubic units as appropriate.

Worked examples

Rectangle area

Example: length 8, width 3
  1. Area of a rectangle is length times width.
  2. Substitute 8 and 3.
  3. Use square units.
Answer: 24 square units

Midpoint

Example: \((2,4)\) and \((8,10)\)
  1. Average the x-values.
  2. Average the y-values.
  3. Write the ordered pair.
Answer: \((5,7)\)
Try one before moving on
Try: Find the area of a rectangle with length 9 and width 4.
Answer: 36 square units.
Next step: do the matching worksheet or quiz while the method is still fresh, then come back and explain the first step in your own words.
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Watch this practice video for additional examples and reinforcement:


Related Topics

Step by step guide to solve Pythagorean Theorem problems

  • We can use the Pythagorean Theorem to find a missing side in a right triangle.
  • In any right triangle: \(\color{blue}{a^2+b^2= c^2}\)

For education statistics and research

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The Pythagorean Theorem – Example 1:

Right triangle ABC has two legs of lengths \(9\) cm (AB) and \(12\) cm (AC). What is the length of the third side (BC)?

Solution:

Use Pythagorean Theorem: \(\color{blue}{a^2+b^2= c^2}\)
Then: \(a^2+b^2= c^2 →9^2+12^2= c^2 →81+144=c^2\)
\(c^2=225 →\) \(c=\sqrt{225}=15\) \(\text{ cm }\) → \(c=15 \text{ cm }\)

The Pythagorean Theorem – Example 2:

Find the hypotenuse of the following right triangle.

Solution:

Use Pythagorean Theorem: \(\color{blue}{a^2+b^2= c^2}\)
Then: \(a^2+b^2= c^2 →8^2+6^2= c^2 →64+36=c^2\)
\(c^2=100 →\) \(c=\sqrt{100}=10\) → \(c=10\)

The Pythagorean Theorem – Example 3:

Find the hypotenuse of the following right triangle.

Solution:

Use Pythagorean Theorem: \(\color{blue}{a^2+b^2= c^2}\)
Then: \(a^2+b^2= c^2 →3^2+4^2= c^2 →9+16=c^2\)
\(c^2=25 →\) \(c=\sqrt{25}=5\) → \(c=5\)

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The Pythagorean Theorem – Example 4:

Right triangle ABC has two legs of lengths \(6\) cm (AB) and \(8\) cm (AC). What is the length of the third side (BC)?

Solution:

Use Pythagorean Theorem: \(\color{blue}{a^2+b^2= c^2}\)
Then: \(a^2+b^2= c^2 →6^2+8^2= c^2 →36+64=c^2\)
\( c^2=100 →\) \(c=\sqrt{100}=10\) \(\text{ cm }\) → \(c= 10 \text{ cm }\)

Exercises for Solveing the Pythagorean Theorem

Find the missing side in each right triangle.

Download Pythagorean Relationship Worksheet

  1. \(\color{blue}{13}\)
  2. \(\color{blue}{5}\)
  3. \(\color{blue}{15}\)
  4. \(\color{blue}{8}\)

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