Finding the Base
Part of the Triangles section of Coddy's Geometry journey. Lesson 26 of 71.
The same equation can be solved for the base instead. For area 21 with a height of 7:
Area 21 and height 7, base unknown
21 = 1/2 × b × 7
21 = 7/2 × b
b = 6
Here the half and the 7 multiply together to give 7/2. Then divide both sides by 7/2 to get b. You can also double both sides first, which gives 42 = 7b, and then divide by 7. Both routes take one multiplication and one division and give the same answer.
Challenge
A triangle has area 30 and height 6.
Find its base b.
Try it yourself
Solve for b
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
All lessons in Triangles
1Sides and Names
Three Sides, Three CornersSorting by SidesNaming by AnglesTicks into EquationsThe Longest SideRecap: Sorting Triangles2The Triangle Inequality
Can Three Sticks Meet?Exactly ReachingHow Short Can It Be?How Long Can It Be?The Range of the Third SideThe FormulaWhole-Number SidesRecap: The Third Side5The Hypotenuse
Squares on the SidesFinding the HypotenusePythagorean TriplesWhen It Is Not WholeSimplifying the RootRecap: The Hypotenuse8Special Right Triangles
The 45-45-90 TriangleLegs from the HypotenuseThe 30-60-90 TriangleAll Three SidesWhich Triangle Is It?Recap: Special Triangles11Mixing Area and Pythagoras
Height of an IsoscelesArea from the HeightThe Equilateral TriangleRight Triangle PerimeterRecap: Two Tools3Perimeter
Around the EdgeA Missing SideIsosceles PerimeterEquilateral PerimeterSides as ExpressionsWrite the PerimeterRecap: Around the Edge6Finding a Leg
Working BackwardsThe LadderWhich Side Is c?A Leg That Is Not WholeRecap: Finding a Leg