A triangle is exactly half of a rectangle (or parallelogram) with the same base and height. So triangle area is base × height, then take half. The feeder skills are rectangle area and halving a number — get them warm and the triangle formula feels obvious.
These are words you'll need to already know to follow this lesson — not the new words the lesson teaches. Review each one, its meaning, and the example so the new lesson makes sense from the start.
Level 1 To add the same number many times to find a total.
Example: 6 × 4 means add 6 four times, which equals 24.
Level 1 How much flat space is inside; you find it by base times height.
Example: A rectangle 8 by 5 has area 8 × 5 = 40 square units.
Level 1 One of two equal parts; the same as dividing by 2.
Example: Half of 24 is 12, because 24 ÷ 2 = 12.
Level 1 To split a number into equal groups.
Example: 24 ÷ 2 splits 24 into two equal parts of 12.
These check the skills you'll need for this lesson — not the new lesson itself. Answer all 3, then press Show my path. No grade — it just suggests where to start.
1. What is 6 × 4?
2. What is half of 24?
3. A rectangle is 8 by 5. What is its area?
Vocabulary previewed and basics checked. Time to start the lesson.
Start Lesson 5-3 →