TL;DR: Online tools can check arithmetic. They cannot replace the setup line. Write the formula in words, substitute the numbers, then compute. A screenshot without a setup is a receipt for a purchase the teacher did not authorize. A setup without a compute can still earn method points when the arithmetic wobbles.
The three-line minimum
Line 1: “percent = part/whole × 100” or “change/old × 100” or “P/100 × N,” named. Line 2: substitute, with units: 12 children / 40 children × 100. Line 3: 30%. If you used a calculator, a fourth optional line: “checked with labeled part/whole fields.” Optional. The first three are the assignment even when devices are allowed.
Teachers who ban phones still want lines 1–3. Teachers who allow phones still want them because 30% without a whole is not inspectable. Inspectability is the point of showing work, not handwriting as a virtue.
What not to copy from a website
Do not paste the entire HTML of a result page. Do not cite “according to the internet” as a reason 12/40 is 30. The reason is the definition. The site agrees because it implements the definition, not because it is an authority above it. Citing the site as authority trains you to lose the definition when the site is down.
Do not copy another student’s screenshot of a different mode. Modes are questions. A correct 70% decrease is the wrong question’s right arithmetic. Your line 1 must match the worksheet’s sentence.
When the tool and the paper disagree
That disagreement is the most valuable work you can show. Write both numbers, then a fifth line: “I swapped part and whole on the site” or “I used % key on 40.” Graders love a found error more than a mysterious 30. A mysterious 30 might be copied. A diagnosed 3000% → 30 is thinking.
If you cannot find the mismatch, you are not done. Do not pick the website because it looks official. Official-looking 4.5 on an 18%-of-250 problem is still outside the 10% fence. Fence then diagnose.
Group work and identical screenshots
Four identical screenshots with no setups look like four phones and one brain. Four setups with the same 30% look like a class that learned a definition. If you collaborate, collaborate on naming the whole, then compute separately. Shared wholes, private arithmetic, compared 30s. That is a group. Shared JPEGs are a stack of paper.
If the LMS has a comment box, paste the three lines as text, not as an image that a grader cannot copy into a key. Images of work with bad contrast fail at 11 p.m. on a phone. Text does not.
Allowed vs honest
If the syllabus bans calculators, using a website is a honesty problem, not a math one. This article will not help you hide a tab. If calculators are allowed but “must show work,” the site is a checker. Checkers sit after line 2. Before line 2 they are ghostwriters. Ghostwriters get 0 on method even when 30% is right.
For take-home work, a sentence “computed 0.18 × 250 by hand, verified on findpercentagecalculator.net” is enough attribution. You do not need a bibliography for 45. You need the 0.18.
Building a habit that survives the next app
Apps change labels. “Amount” vs “part” vs “value.” Your words “part” and “whole” do not have to match the UI, but you must map them on paper: “site’s Total = my whole = 40 attempts.” Mapping is showing work for the 2020s. Without a map, you will fill Total with 12 because it was first. First boxes are not wholes. Sentences are.
Practice the three lines on easy 10/50 = 20% until they are boring. Boring setups are how hard setups stay honest when the numbers get ugly. Ugly numbers deserve the same three lines, not fewer because you were tired. Tired is when 3000% sneaks in and you submit because the JPEG was already taken.
Partial credit that screenshots cannot earn
A grader who can see 12/40 × 100 can give points when you multiply 12×100 first and then divide by 40 wrong. A JPEG of 0.3% cannot. If you must screenshot, screenshot the three text lines in a notes app, not the glowing button. Buttons do not carry substitutions. Substitutions are where 40 became 4.
For digital handwritten, photograph in order: formula, substitute, boxed answer, then optional site check. Out-of-order photos get read as four problems. Order is part of showing work. So is a boxed whole: draw a square around 40 children. Squares are cheap and they mark the base for the person who grades at midnight.
Oral exams and the setup you can say
If you might be asked at the board, the three lines must be speakable in one breath each. “Part over whole times 100. Twelve over forty times 100. Thirty percent.” That is showing work without paper. A URL is not speakable as a reason. You can say you checked a calculator after. You cannot say the calculator is why 40 is the whole. Why is the sentence “attempts, not minutes.” Practice the because-clause. That is the oral version of showing work.
