--- title: "#math articles | Hashnode" description: "Explore 320 articles tagged #math on Hashnode. Tutorials, guides, and how-tos from the community." url: "https://hashnode.com/tag/math" --- Tag # #math 320 posts · 118 followers [Sebastian Bardach](https://hashnode.com/@bardachtech) · [3h ago](https://hashnode.com/posts/effective-hourly-rate-on-a-retainer-explained-the-formula-that-shows-when-a-client-stops-paying/6af8bed5194a477ff86a12b0) ### [Effective hourly rate on a retainer, explained: the formula that shows when a client stops paying](https://bardachtech.hashnode.dev/effective-hourly-rate-on-a-retainer-explained-the-formula-that-shows-when-a-client-stops-paying?utm_source=hashnode&utm_medium=feed) A monthly retainer has a contracted rate (fee ÷ hours included) and an effective rate (fee ÷ hours actually used). The contract shows the first. Your margin depends on the second. The formula effectiv 3 min read · [bardachtech.hashnode.dev](https://bardachtech.hashnode.dev/effective-hourly-rate-on-a-retainer-explained-the-formula-that-shows-when-a-client-stops-paying?utm_source=hashnode&utm_medium=feed) [Sebastian Bardach](https://hashnode.com/@bardachtech) · [21h ago](https://hashnode.com/posts/the-freelance-hourly-rate-formula-explained-one-division-and-the-input-that-moves-it-most/6af7c2d8ecb2109c710096b0) ### [The freelance hourly rate formula, explained: one division and the input that moves it most](https://bardachtech.hashnode.dev/the-freelance-hourly-rate-formula-explained-one-division-and-the-input-that-moves-it-most?utm_source=hashnode&utm_medium=feed) A freelance hourly rate is one division: the revenue you need over a year, divided by the hours a client will actually pay for. Both halves have a trap, and the second one is where most rates go wrong 3 min read · [bardachtech.hashnode.dev](https://bardachtech.hashnode.dev/the-freelance-hourly-rate-formula-explained-one-division-and-the-input-that-moves-it-most?utm_source=hashnode&utm_medium=feed) [Zayed](https://hashnode.com/@zayed-clearcalc) · [2d ago](https://hashnode.com/posts/reverse-sales-tax-how-to-find-the-pre-tax-price-from-a-receipt-total-with-javascript/6af53fe7c449419ead83e895) ### [Reverse sales tax: how to find the pre-tax price from a receipt total (with JavaScript)](https://clearcalc-notes.hashnode.dev/reverse-sales-tax-how-to-find-the-pre-tax-price-from-a-receipt-total-with-javascript?utm_source=hashnode&utm_medium=feed) Disclosure: I'm Zayed and I build ClearCalc Tools, a free calculator site. This post explains the math behind one of its features. A very common mistake when you want the price before tax is to subtra 2 min read · [clearcalc-notes.hashnode.dev](https://clearcalc-notes.hashnode.dev/reverse-sales-tax-how-to-find-the-pre-tax-price-from-a-receipt-total-with-javascript?utm_source=hashnode&utm_medium=feed) [FightNome](https://hashnode.com/@fightnome) · [3d ago](https://hashnode.com/posts/random-calls-on-a-beat-grid-the-arithmetic-of-6-to-45-calls-per-minute-at-74-to-128-bpm/6af474b647d7c8e38b2cb349) ### [Random calls on a beat grid: the arithmetic of 6 to 45 calls per minute at 74 to 128 BPM](https://fightnome.hashnode.dev/random-calls-on-a-beat-grid-the-arithmetic-of-6-to-45-calls-per-minute-at-74-to-128-bpm?utm_source=hashnode&utm_medium=feed) I build FightNome, a boxing and Muay Thai training app, and this note comes from working on one of its modes. FightNome has two striking modes. In combo mode the coach repeats a combination you built. 4 min read · [fightnome.hashnode.dev](https://fightnome.hashnode.dev/random-calls-on-a-beat-grid-the-arithmetic-of-6-to-45-calls-per-minute-at-74-to-128-bpm?utm_source=hashnode&utm_medium=feed) [CalcHub Tools](https://hashnode.com/@calchubtools) · [3d ago](https://hashnode.com/posts/voltage-drop-explained-with-code-why-your-100-foot-extension-run-needs-thicker-wire/6af440cf6953dab38100fc76) ### [Voltage drop, explained with code: why your 100-foot extension run needs thicker wire](https://calchubtools.hashnode.dev/voltage-drop-explained-with-code-why-your-100-foot-extension-run-needs-thicker-wire?utm_source=hashnode&utm_medium=feed) Ohm's law, a resistance table and one line of JavaScript explain voltage drop. Here's how to calculate it, why the 3% guideline exists, and how to pick a wire gauge for long runs. 4 min read · [calchubtools.hashnode.dev](https://calchubtools.hashnode.dev/voltage-drop-explained-with-code-why-your-100-foot-extension-run-needs-thicker-wire?utm_source=hashnode&utm_medium=feed) [Ravi Patel](https://hashnode.com/@ravi-numerics) · [4d ago](https://hashnode.com/posts/a-numerically-stable-quadratic-solver-in-python-with-steps/6af2f6002304557863f4c833) ### [A Numerically Stable Quadratic Solver in Python (with Steps)](https://ravi-numerics.hashnode.dev/a-numerically-stable-quadratic-solver-in-python-with-steps?utm_source=hashnode&utm_medium=feed) Most "quadratic formula" snippets online stop at two lines of code. That is fine until you hit a negative discriminant, a = 0, or floating-point noise that turns a double root into two slightly differ 3 min read · [ravi-numerics.hashnode.dev](https://ravi-numerics.hashnode.dev/a-numerically-stable-quadratic-solver-in-python-with-steps?utm_source=hashnode&utm_medium=feed) [Urban Mixo](https://hashnode.com/@urbanmixo) · [5d ago](https://hashnode.com/posts/how-does-a-grade-calculator-work-the-linear-algebra-of-weighted-scoring-and-final-exam-targets/6af1f2c7b5f1ae3493befcdd) ### [How Does a Grade Calculator Work? The Linear Algebra of Weighted Scoring and Final Exam Targets](https://urbanmixo.hashnode.dev/how-does-a-grade-calculator-work-the-linear-algebra-of-weighted-scoring-and-final-exam-targets?utm_source=hashnode&utm_medium=feed) A mathematical breakdown of weighted syllabus equations, credit-hour quality points, and exam target prediction algorithms in vanilla JavaScript. 9 min read · [urbanmixo.hashnode.dev](https://urbanmixo.hashnode.dev/how-does-a-grade-calculator-work-the-linear-algebra-of-weighted-scoring-and-final-exam-targets?utm_source=hashnode&utm_medium=feed) [2](https://hashnode.com/posts/how-does-a-grade-calculator-work-the-linear-algebra-of-weighted-scoring-and-final-exam-targets/6af1f2c7b5f1ae3493befcdd) [Urban Mixo](https://hashnode.com/@urbanmixo) · [5d ago](https://hashnode.com/posts/from-formula-to-pixels-building-a-60-fps-mathematical-graphing-engine-on-html5-canvas-in-pure-javascript/6af1ec6240651d1a0fa8d90c) ### [From Formula to Pixels: Building a 60 FPS Mathematical Graphing Engine on HTML5 Canvas in Pure JavaScript](https://urbanmixo.hashnode.dev/from-formula-to-pixels-building-a-60-fps-mathematical-graphing-engine-on-html5-canvas-in-pure-javascript?utm_source=hashnode&utm_medium=feed) How we solved safe algebraic evaluation without eval(), world-to-screen coordinate mapping, and asymptote discontinuity handling in under 100 lines of code. 9 min read · [urbanmixo.hashnode.dev](https://urbanmixo.hashnode.dev/from-formula-to-pixels-building-a-60-fps-mathematical-graphing-engine-on-html5-canvas-in-pure-javascript?utm_source=hashnode&utm_medium=feed) [CalcHub Tools](https://hashnode.com/@calchubtools) · [5d ago](https://hashnode.com/posts/sizing-a-solar-array-from-your-electric-bill-the-math-in-a-dozen-lines-of-javascript/6af19dbbb5e779f27e8dbd2f) ### [Sizing a solar array from your electric bill: the math, in a dozen lines of JavaScript](https://calchubtools.hashnode.dev/sizing-a-solar-array-from-your-electric-bill-the-math-in-a-dozen-lines-of-javascript?utm_source=hashnode&utm_medium=feed) How to turn monthly kWh into a system size and a panel count, what 'peak sun hours' really means, and the derate factor most quick estimates leave out. 4 min read · [calchubtools.hashnode.dev](https://calchubtools.hashnode.dev/sizing-a-solar-array-from-your-electric-bill-the-math-in-a-dozen-lines-of-javascript?utm_source=hashnode&utm_medium=feed) [Sigma Calculator](https://hashnode.com/@sigmacalculator) · [6d ago](https://hashnode.com/posts/how-a-car-loan-calculator-works-the-math-behind-your-monthly-payment/6af0d7b65f1ba47de6248be0) ### [How a Car Loan Calculator Works — The Math Behind Your Monthly Payment](https://sigmacalculator.hashnode.dev/how-a-car-loan-calculator-works-the-math-behind-your-monthly-payment?utm_source=hashnode&utm_medium=feed) You type four numbers into a car loan calculator — price, down payment, interest rate, term — and it instantly tells you the monthly payment. No magic. Just one formula, written in 1676, doing exactly 3 min read · [sigmacalculator.hashnode.dev](https://sigmacalculator.hashnode.dev/how-a-car-loan-calculator-works-the-math-behind-your-monthly-payment?utm_source=hashnode&utm_medium=feed) [1](https://hashnode.com/posts/how-a-car-loan-calculator-works-the-math-behind-your-monthly-payment/6af0d7b65f1ba47de6248be0)