Water and wastewater · Worked step by step
What is the area of a 25 foot round tank?
If math has never been your thing, you are in the right place. Try it on paper first, then we write it out with you, one small step at a time, and explain every step in plain words so you never lose the thread.
The problem
A round tank is 25 feet across. What is its floor area?
Grab a pen and paper first
Give it a real try on paper before you watch. If you get stuck, take a hint. If you go blank, that is fine, press play and we will walk it through together.
Watch it solved, with you
Every step is written out slowly and explained in plain words, so you always know what just happened. Nobody skips ahead and leaves you behind.
Press play and I’ll write it out with you, one small step at a time.
Every step gets a plain-words explanation here, so you always know exactly what just happened and why.
The written version, step by step
- 1
Square the width
25 × 25 = 625
- First multiply the width by itself.
- 25 × 25 = 625.
- Now take the circle share of that.
- 2
Take the circle share
area = 625 × 0.785 • area = 490.6 ≈ 491 sq ft
- Multiply 625 by 0.785.
- That is about 490.6.
- So the area is about 491 square feet.
Quick trick: 0.785 is close to 0.8, so a quick estimate is 625 × 0.8 = 500.
Remember this for good
The area of a circle is 0.785 times across times across, in square feet.
0.785 is the circle factor. Square the width, then take about 78.5% of it.
Solve it fast next time
- Round area = 0.785 times across times across.
- Square the width first, then multiply by 0.785.
- Across is the diameter, not the radius.
The answer: About 491 square feet.