Wastewater · Worked step by step
What percent of the TSS was removed, 240 to 60?
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
Wastewater comes in with TSS of 240 mg/L and leaves with 60 mg/L. What percent of the TSS was removed?
Grab a pen and paper first
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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
Find how much was removed
removed = 240 - 60 • removed = 180 mg/L
- In at 240, out at 60.
- The difference is what got removed.
- 240 - 60 = 180 mg/L.
Quick trick: Removed is always in minus out. Subtract first.
- 2
Divide by the start, make a percent
180 ÷ 240 = 0.75 • 0.75 × 100 = 75%
- Divide removed by the starting amount: 180 ÷ 240 = 0.75.
- Times 100 to make it a percent.
- So 75% of the TSS was removed.
Quick trick: 180 ÷ 240 is the same as 3 ÷ 4 = 0.75. Simplify before dividing.
Remember this for good
Percent removed = (amount taken out divided by amount you started with) times 100.
Removed over started, times 100. You took out 180 of the original 240; 180 of 240 is three quarters, which is 75%.
Solve it fast next time
- Subtract first to find how much was removed, then divide by the starting (in) number.
- Always divide by the IN value, never the leftover.
- Times 100 at the end for a percent.
The answer: 75% removed.