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Slant height of a Frustum of a Cone
l = √(h² + (R − r)²)
Where: R = bottom radius, h = height, l = slant height, r = top radius
Use the same units for all lengths (e.g. all in cm); areas come out in cm², volumes in cm³.
Solved example
Given: R = 7, h = 5, r = 10
Find: l (slant height)
- Formula: l = √(h² + (R - r)²)
- Substitute the values: l = √(5² + (-10 + 7)²)
- Result: l = 5.830952
Answer: l = 5.830952
Calculator
How to calculate Slant height of a Frustum of a Cone
- Write down the formula: l = √(h² + (R − r)²).
- Note the known values (R, h, r).
- Substitute them and simplify to find l.
- Use the calculator above to solve for any letter.
Frequently asked questions
What is the formula for Slant height of a Frustum of a Cone?
The formula is l = √(h² + (R − r)²), where R = bottom radius, h = height, l = slant height, r = top radius.
What is Slant height of a Frustum of a Cone when R = 7, h = 5, r = 10?
l = 5.830952. Substitute the values into l = √(h² + (R − r)²) and simplify.