Volume of a cone
Use V = (1/3)πr²h for a cone with radius 3 and height 7.
A cone holds exactly one third of the cylinder with the same base and height. With r = 3 and h = 7: V = (1/3) × π × 9 × 7 = 21π, about 65.97.
Classic Graphing 84
Start on the main screen: Press 2nd then mode (QUIT) to get back to the home screen. Pressing clear on a menu also backs out of it.
Type (1 ÷ 3) × π × 3² × 7. Brackets keep the one third together.
(1÷3)×2ndπ^×3x²×7Press enter.
enter
You should see(1/3)*π*3²*7 65.97344573
Classic Graphing 84 key reference · Classic Graphing 84 manual
Natural Scientific 991
Start on the main screen: Press MENU, then 1 (Calculate) to return to the main calculation screen. AC clears the line you are on.
Make the fraction 1 over 3 and step out of it. Multiply by π, then 3 squared, then 7.
/1▼3▶×SHIFTπ×10ˣ×3x²×7Press = and then S⇔D for the decimal.
=S⇔D
You should see65.97344573
Natural Scientific 991 key reference · Natural Scientific 991 manual
RPN Scientific 15
Start on the main screen: There is no menu to leave. Press the back arrow to clear a number you are typing, or CLx (g then back arrow) to clear the X register.
Square the radius: 3, g, x². Multiply by the height 7.
3gx²√x7×Multiply by π (g EEX) and divide by 3.
gπEEX×3÷
You should see65.9734
Tips
- Use the height straight up from the base, not the slanted side.