Ticks into Equations

Part of the Triangles section of Coddy's Geometry journey. Lesson 7 of 60.

The same tick marks mean the same length. Sometimes a side with a tick has a letter in its label. Then you can write an equation.

$Triangle PQR: sides QR and RP each carry one tick, labelled 2x plus 1 and 13; PQ is 10$

QR and RP have one tick each, so they are equal: $2x+1 = 13$ . Take 1 away from both sides: $2x = 12$ . Divide both sides by 2: $x = 6$ . The side with no tick, 10, is not used.

Challenge

Two sides of △ABC have one tick each: $3x-4$ and 17. Find x. Tap the two sides with ticks and pick the reason. Then solve for x and press Check.

Try it yourself

$Use the figure to find x$

Use the figure to find x

All lessons in Triangles

1The Triangle Inequality

Can Three Sticks Meet?Exactly Reaching The Range of the Third Side Recap: The Third Side

4Area of a Triangle

Half the Rectangle Height Is Not a Side Right Triangle Area Finding the Height Any Side Can Be the Base Recap: Area

7Is It Right?

The Converse Testing a Triangle Acute or Obtuse?Sorting by the Test Recap: Right or Not

10Scale in the World

Shadows Across the River Nested Triangles A Side with an Expression Recap: Scale in the World

2Sides and Names

Sorting by Sides The Longest SideTicks into EquationsRecap: Sorting Triangles

5The Pythagorean Theorem

Squares on the Sides Finding the Hypotenuse Pythagorean Triples When It Is Not Whole Recap: The Hypotenuse

8Special Right Triangles

The 45-45-90 Triangle Legs from the Hypotenuse The 30-60-90 Triangle All Three Sides Which Triangle Is It?Recap: Special Triangles

11Two Tools at Once

Height of an Isosceles Area from the Height The Equilateral Triangle Right Triangle Perimeter Recap: Two Tools