Worksheet generator

1.C — 16KA-0050Working backwards

• AI added the 4 and the 6 and stopped, forgetting to undo the halving.
• BI doubled the 6 first and then added the 4, reversing the steps in the wrong order.
• DI doubled the total at the end rather than doubling only the amount left after the first spend.
• EI doubled twice because spending half felt like it needed undoing more than once.

2.E — Not all birds can flyKA-0146Reading a logical statement precisely

• AI read some cannot as meaning none can, which is a far stronger claim.
• BI chose a statement that directly contradicts the one I was given.
• CI read some as meaning a majority, when it only guarantees at least one.
• DI read some as meaning exactly one, when it means at least one.

3.D — 30KA-0007Working backwards

• AI added the 6 and the 9 and stopped, forgetting to undo the halving at the start.
• BI undid the steps in the order they were written instead of reversing the order as well as the operations.
• CI doubled the 9 first and then added the 6, which reverses the steps in the wrong order.
• EI doubled twice because giving half away felt like it should be undone more than once.

4.C — CalKA-0091Elimination grids

• AI used Bo's clue and forgot the very first clue, which rules Ana out directly.
• BI read Bo's clue as telling me what Bo has rather than what Bo does not have.
• DI stopped after using each clue once, without going back to see what the ticks had ruled out.
• EI applied Bo's clue but never came back to Ana's, so I left two people in the running.

5.B — BoKA-0092Ordering and ranking from clues

• AI gave the child who is first rather than the one who is second.
• CI placed Cal directly after Ana, reading ahead of Dee as meaning immediately ahead.
• DI built the order backwards from the last position instead of forwards from the first.
• EI assumed the clues left several orders open without checking that they chain into a single one.

6.B — 60KA-0093Weighing and balance puzzles

• AI halved the apple's weight, as if one apple balanced two pears.
• CI assumed a pear must weigh the same as an apple because the two sides balance.
• DI multiplied the apple's weight by three halves the wrong way round, making the pear heavier.
• EI gave the total weight of the two apples rather than the weight of one pear.

7.B — Box X is not redKA-0099Reading a logical statement precisely

• AI read the rule backwards, as if being heavy were what makes a box red.
• CI assumed not red must mean one particular other colour, when the rule says nothing about which.
• DI contradicted the rule I was given rather than applying it to box X.
• EI decided one fact could not settle anything, without testing what would follow if X were red.

8.B — 1KA-0017Truth-tellers and liars

• AI assumed everyone could be lying at once without checking that Cal's statement would then be true.
• CI found one consistent truth-teller and added another without testing whether both could hold together.
• DI assumed everyone was telling the truth without noticing that Ana's statement then contradicts Bo's.
• EI gave up after one assumption led to a contradiction, instead of trying the other assumption.

9.E — No, because the colours do not balanceKA-0034Coloring arguments

• AI assumed that because 14 is even, seven dominoes must fit somehow.
• BI tried a few arrangements, got most of the board covered, and assumed a full covering existed.
• CI claimed the right answer for the wrong reason, since 14 is in fact divisible by 2.
• DI thought removing a different pair of opposite corners could change the colour balance, but opposite corners always share a colour.

10.B — 2KA-0094Weighing and balance puzzles

• AI assumed one weighing could separate nine possibilities, but it has only three outcomes.
• CI split the coins into halves each time, which wastes the balance's third outcome.
• DI weighed the coins one against another in pairs rather than in groups.
• EI compared each coin with a known good one in turn, which always works but is nowhere near the fewest.

11.B — 9KA-0095The extremal principle

• AI divided 100 by 12 and rounded down instead of up.
• CI rounded the division to a convenient number without checking that a packing with a smaller maximum exists.
• DI gave the number of boxes as the answer rather than a number of apples.
• EI described the case where one box holds everything, which is possible but not guaranteed.

12.D — No, because the number of moves is oddKA-0097Parity arguments

• AI assumed enough moves can undo anything, without asking what each move preserves.
• BI tried a few sequences that nearly worked and assumed a better choice would finish the job.
• CI reached for the number of items rather than for what a single swap actually changes.
• EI thought the choice of swaps could change the outcome, when every swap has the same effect.

13.D — No, because the two colours cannot balanceKA-0101Coloring arguments

• AI checked that 100 divides by 4 and treated that as proof that a covering exists.
• BI assumed a covering must exist somewhere and that I simply had not found it yet.
• CI gave a reason that is not even true, since 100 really is a multiple of 4.
• EI thought orientation could rescue it, but every turn of a T covers the same mixture of colours.

14.D — DeeKA-0136Ordering and ranking from clues

• AI ignored the very first clue, which rules Ana out of the front directly.
• BI put Bo at the front, but Bo must have Ana immediately in front of him.
• CI forgot that Cal is fixed at the back of the line.
• EI stopped once two arrangements seemed possible, without testing whether the second one actually fits every clue.

15.A — It is always oddKA-0167Parity arguments

• BI checked the parity of the count of numbers rather than of their sum.
• CI tried two examples, got different answers, and concluded nothing is forced.
• DI assumed differences must shrink all the way to nothing.
• EI found one sequence of moves ending at 1 and assumed every sequence must.