{"id":"dat-col-utility-split-move-in","audience":"college","category":"data","technique":"context","title":"Split a utilities bill when a roommate moved in mid-month","free":false,"task":"You're splitting October utilities among 3 roommates. Jae moved in on Oct 16, so he pays half a share; Alex and Sam pay full shares. Sam's internet upgrade is his alone. Write exactly 3 numbered lines, one per roommate, each showing the math, for a group chat. Plain text, under 60 words, nothing else.","materialLabel":"October bills (attached to your prompt automatically)","material":"OCTOBER UTILITIES - 418 Linden Ave, Apt 2\n\nElectric (Volta Power) | $120\nInternet (Fibrely) | $60\nWater (city) | $45\nTotal | $225\n\nFibrely bill detail:\n- Base plan 300 Mbps | $45\n- Speed upgrade to 1 Gbps | $15\n(Sam asked for the upgrade for gaming and said he'd cover it.)\n\nGroup chat:\n- Alex: I paid all three bills already, send me your part.\n- Sam: can we do the split by Friday?\n- Jae: just moved in, sorry for the boxes everywhere\n- Alex: also we're out of dish soap\n\nLease note: rent is separate and paid to the landlord directly.\n\nMore notes:\n- Volta Power bills on the 3rd; Fibrely on the 10th.\n- We use a shared notes page for house stuff.","rules":[{"type":"numberedItems","count":3},{"type":"plainText"},{"type":"maxWords","max":60}],"mistakes":[{"title":"Splitting evenly","why":"The AI doesn't know Jae moved in mid-month, so it splits $225 three ways at $75.","fix":"Add: \"Jae moved in Oct 16, so he pays half a share.\"","checks":["r0","r1"]},{"title":"Sharing the upgrade","why":"The AI spreads Sam's $15 upgrade across everyone.","fix":"Add: \"Sam pays the $15 upgrade alone; split the other $210.\"","checks":["r0","r1"]},{"title":"Not asking to see the work","why":"Roommates will question a bare number.","fix":"Add a line to copy: \"1. Alex: $210 ÷ 2.5 = $84\"","checks":["r2","numberedItems"]},{"title":"Trusting the AI to count words","why":"AI is bad at counting. Ask for a total word limit and it often lands over it.","fix":"Cap each line: \"each line under 14 words.\"","checks":["maxWords"]},{"title":"Forgetting where it goes","why":"AI loves markdown tables and bold, which show up as clutter in a group chat.","fix":"Add: \"Plain text, no bold, headings or tables.\"","checks":["plainText"]}],"promptHints":[{"label":"Explains the half share","patterns":["half","moved in","16","2\\.5"]},{"label":"Handles the upgrade","patterns":["upgrade","sam.{0,30}15|\\$15"]},{"label":"Asks to show the math","patterns":["show (the |your )?(math|work)","x \\$|\\bx\\b.{0,10}=","calculation","step"]},{"label":"Sets a word limit","patterns":["\\d+\\s*words","word (limit|count)","under \\d+"]},{"label":"Asks for plain text","patterns":["plain","no bold","no markdown","no formatting","no (headings|tables)"]}],"hint":"The AI can't know who moved in when. Tell it how the shares work and what Sam pays alone, and ask for the math on each line.","rubricLabels":["Splits the shared $210 ($225 minus Sam's $15 upgrade) over 2.5 shares: $84 per full share","Alex owes $84, Sam owes $99 ($84 + $15 upgrade) and Jae owes $42 (half share)","Each line shows its math (for example $210 ÷ 2.5 = $84), and there is no intro or closing chatter"]}