Place Value Games: Keep the Zero Column

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<body class="classroom"><main><header><div class="eyebrow">Classroom practice · fictional data</div><h1>Place Value Games: Keep the Zero Column</h1><p>Removing the zero from 305 gives 35, changing the three from hundreds to tens. <mark>No tens still needs a tens position</mark> in the numeral.</p></header>
<nav><button type="button" id="pv1">305</button><button type="button" id="pv2">350</button><button type="button" id="pv3">503</button><button type="button" id="reset">Reset</button></nav><h2 id="numeral"></h2><div id="model" class="tokens"></div><label for="h">Hundreds count</label><input id="h" type="text" value=""><label for="t">Tens count</label><input id="t" type="text" value=""><label for="o">Ones count</label><input id="o" type="text" value=""><label for="p5">Position of 5 (Hundreds, Tens, Ones)</label><input id="p5" type="text" value=""><label for="v5">Value of 5</label><input id="v5" type="text" value=""><label for="p3">Position of 3</label><input id="p3" type="text" value=""><label for="v3">Value of 3</label><input id="v3" type="text" value=""><nav><button type="button" id="check">Check seven answers</button></nav><p id="result" class="result" role="status"></p><div id="ledger" class="ledger"></div>
<footer>Reset clears completed-card history and returns to unanswered fields for 305.</footer></main><script>
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(function(){const keys=[[305,3,0,5,'ones',5,'hundreds',300],[350,3,5,0,'tens',50,'hundreds',300],[503,5,0,3,'hundreds',500,'ones',3]];let index=0;const done=new Set(),ids=['h','t','o','p5','v5','p3','v3'],answerLabels={h:'Hundreds count',t:'Tens count',o:'Ones count',p5:'Position of 5',v5:'Value of 5',p3:'Position of 3',v3:'Value of 3'};function choose(i){index=i;set('numeral',String(keys[i][0]));q('model').innerHTML=['Hundreds','Tens','Ones'].map((labelName,j)=>'<section><h3>'+labelName+': '+keys[i][j+1]+'</h3><p>'+Array.from({length:keys[i][j+1]},()=>j===0?'▦100':j===1?'▰10':'●1').join(' ')+'</p><p>Contribution '+(keys[i][j+1]*[100,10,1][j])+'</p></section>').join('');for(const id of ids)q(id).value='';set('result','Not checked. Zero is an answer; blank is unanswered.');set('ledger',`${done.size} of 3 unique cards checked correctly. Extension: 2 hundreds + 10 tens + 5 ones =305.`);}for(let i=0;i<3;i++)on('pv'+(i+1),()=>choose(i));for(const id of ids)q(id).addEventListener('input',()=>set('result','Answers changed; check again.'));on('check',()=>{const vals=ids.map(id=>q(id).value.trim().toLowerCase());if(vals.some(v=>v===''))return set('result','Complete all seven answers; use 0 where needed.');const bad=vals.map((v,i)=>v!==String(keys[index][i+1])?answerLabels[ids[i]]:null).filter(Boolean);if(bad.length)return set('result','Review '+bad.join(', ')+'. Position names and values are different answers.');done.add(index);set('result','Matching counts, positions and values. '+keys[index][0]+' = '+(keys[index][1]*100)+' + '+(keys[index][2]*10)+' + '+keys[index][3]+'.');set('ledger',`${done.size} of 3 unique cards checked correctly.`);});on('reset',()=>{done.clear();choose(0);});choose(0);})();})();
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