135 minutes. Two clear formats.

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4px}.mobile-label{display:block;font-size:11px;font-weight:750;color:#52636a}.cell{padding:12px}.cell-grid{gap:8px}.readiness{grid-template-columns:1fr;gap:3px}.rhythm-grid{grid-template-columns:65px repeat(4,1fr);gap:2px}.rhythm-grid>*{font-size:11px;padding:12px 2px}.ribbon{grid-template-columns:57px 1fr 48px;gap:6px}}@media print{main{max-width:none;padding:0}body{background:#fff}button,.actions{display:none}.view[hidden]{display:block!important}.paper{break-inside:avoid}}</style></head><body class=""><main><header><span class="eyebrow">Duration converter · nonnegative whole minutes</span><h1>135 minutes. Two clear formats.</h1><p>135 ÷ 60 = 2.25 decimal hours. The same duration is 2 hours 15 minutes. Decimal .25 means a quarter of an hour, not 25 minutes.</p><span class="fiction">Original illustrative example · local review copy; not an official record</span></header><section class="paper"><label for="minutes">Total duration in whole minutes</label><input id="minutes" type="text" inputmode="numeric" value="135" aria-describedby="input-help"><p id="input-help" class="muted">Duration, not clock time. Whole minutes only. Values above 24 hours do not wrap.</p><div class="actions"><button data-preset="90">90 minutes</button><button data-preset="135">135 minutes</button><button data-preset="0">Zero</button><button data-preset="1500">1,500 minutes</button><button id="clear">Clear</button></div><div class="pair"><div class="metric"><small>Decimal hours · rounded to 2 decimals</small><p id="decimal" class="large">2.25</p><p>hours</p></div><div class="metric secondary"><small>Whole hours + remaining minutes</small><p id="duration" class="large" style="font-size:36px">2 h 15 m</p><p>Same duration</p></div></div><p id="feedback" class="feedback" role="status"></p><p id="formula" class="formula"></p></section><aside class="note"><strong>1.30 is a different decimal duration</strong><p>1.30 decimal hours × 60 = 78 minutes.<br>1 hour 30 minutes = 90 minutes = 1.5 decimal hours.<br>Neither is a clock reading such as 1:30 p.m.</p></aside><table><thead><tr><th scope="col">Minutes</th><th scope="col">Decimal hours</th><th scope="col">Hours/minutes</th></tr></thead><tbody><tr><td><span class="mobile-label">Minutes</span>90</td><td><span class="mobile-label">Decimal hours</span>1.5</td><td><span class="mobile-label">Hours/minutes</span>1 hour 30 minutes</td></tr><tr><td><span class="mobile-label">Minutes</span>135</td><td><span class="mobile-label">Decimal hours</span>2.25</td><td><span class="mobile-label">Hours/minutes</span>2 hours 15 minutes</td></tr><tr><td><span class="mobile-label">Minutes</span>0</td><td><span class="mobile-label">Decimal hours</span>0</td><td><span class="mobile-label">Hours/minutes</span>0 hours 0 minutes</td></tr><tr><td><span class="mobile-label">Minutes</span>1,500</td><td><span class="mobile-label">Decimal hours</span>25</td><td><span class="mobile-label">Hours/minutes</span>25 hours 0 minutes</td></tr></tbody></table><p class="muted">Full calculation precision is retained before display formatting. Display rounding does not decide billing or payroll rules.</p><footer>Changes and practice answers last only on this page. Keep actual observations, decisions and records in your established school, document or spreadsheet workflow.</footer></main><script>const $=id=>document.getElementById(id);const esc=s=>String(s).replace(/[&<>"']/g,c=>({'&':'&amp;','<':'&lt;','>':'&gt;','"':'&quot;',"'":'&#39;'}[c]));const status=s=>{$('feedback').textContent=s;};
function convert(raw){if(raw.trim()==='')return {error:'Enter minutes. Blank is different from zero.'};if(!/^\d+$/.test(raw.trim()))return {error:'Use nonnegative whole minutes, not negative/fractional values or 1:30.'};const minutes=Number(raw.trim());if(!Number.isSafeInteger(minutes))return {error:'Duration exceeds the exact whole-number range.'};return {minutes,hours:minutes/60,whole:Math.floor(minutes/60),remainder:minutes%60};}function render(){const r=convert($('minutes').value);$('minutes').setAttribute('aria-invalid',String(Boolean(r.error)));if(r.error){$('decimal').textContent='—';$('duration').textContent='—';$('formula').textContent='No conversion performed.';status(r.error);return;}$('decimal').textContent=r.hours.toFixed(2);$('duration').textContent=r.whole+' h '+r.remainder+' m';$('formula').textContent=r.minutes+' ÷ 60 = '+r.hours+' hours before display rounding; '+r.minutes+' − '+r.whole+' × 60 = '+r.remainder+' remaining minutes.';status('Converted '+r.minutes+' whole minutes. Decimal display is rounded to two decimals.');}$('minutes').addEventListener('input',render);document.querySelectorAll('[data-preset]').forEach(b=>b.addEventListener('click',()=>{$('minutes').value=b.dataset.preset;render();}));$('clear').addEventListener('click',()=>{$('minutes').value='';render();$('minutes').focus();});globalThis.Model={convert};render();</script></body></html>