Right-angled triangle — The area is 10 sq cm. If the perpendicular (height) is 20 cm, find the base.

Introduction / Context:
For a right triangle, area = 1/2 * base * height. When area and one leg are known, the other leg can be computed directly. Units are in centimeters.

Given Data / Assumptions:

• Area = 10 sq cm
• Perpendicular (height) = 20 cm

Concept / Approach:
Use height * base with the 1/2 factor. Solve base = (2 * Area) / height.

Step-by-Step Solution:
base = (2 * 10) / 20 = 20 / 20 = 1 cm

Verification / Alternative check:
Plug back: area = 1/2 * 1 * 20 = 10 sq cm ✔

Why Other Options Are Wrong:
2, 3, 4, 5 cm all produce areas 20, 30, 40, 50 divided by 2, not equal to 10 with the given height.

Common Pitfalls:
Missing the factor 1/2 or confusing base and height values.

Final Answer:
1 cm