Worksheet generator

1.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.

2.D — 16KA-0033Means, and working backwards from a mean

• AI subtracted the two means from each other and gave the difference as the removed number.
• BI assumed the removed number must be the new mean, since the mean dropped to 11.
• CI assumed removing a number equal to the old mean is what changes the mean.
• EI added the two totals instead of subtracting one from the other.

3.B — 3KA-0068Tree diagrams

• AI read the two in exactly two heads as the answer rather than as a condition to count.
• CI counted the outcomes with two or more heads, so I included the three-head one as well.
• DI counted the orderings of three different objects instead of listing the eight outcomes.
• EI gave the total number of possible outcomes rather than the number with exactly two heads.

4.D — 6KA-0085Line and rotational symmetry

• AI checked only the vertical and horizontal folds and stopped there.
• BI counted the lines through opposite corners and forgot the ones through opposite edges.
• CI assumed a hexagon behaves like a rectangle with a couple of extra folds.
• EI counted each line twice, once from each end.

5.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.

6.B — 8KA-0100Working backwards

• AI undid the operations in the order they were written instead of in reverse order.
• CI gave the final answer back, assuming the three steps cancelled each other out.
• DI doubled the 11 and subtracted the 6 but forgot the final halving that undoes the doubling.
• EI undid only the halving and stopped there without touching the other two steps.

7.C — 65KA-0103Recursive rules

• AI stopped at the fourth term, counting the starting number as the first step rather than the first term.
• BI generated one term too few, giving the fifth term instead of the sixth.
• DI doubled six times and subtracted 1 only once at the end.
• EI generated one term too many, giving the seventh instead of the sixth.

8.B — 21.5KA-0115Multi-step arithmetic word problems

• AI halved the 60 pencils before giving any away.
• CI subtracted 17 from one box of 12 rather than from the whole 60.
• DI gave the number of pencils left over rather than what each child gets.
• EI gave the starting number of pencils without doing either of the steps.

9.D — 21KA-0132Eliminate impossible choices by bounding

• AI did not try one five and four twos, so I judged this total impossible.
• BI missed the combination of two fives and three twos.
• CI stopped listing after two fives and never reached three fives and two twos.
• EI forgot the case where every coin is a five, which is allowed by the wording.

10.B — 50 sq cmKA-0164Scaling and similar figures

• AI scaled the area by 5/3, using the side ratio directly instead of its square.
• CI multiplied the area by 2.5, halfway between the side ratio and its square.
• DI scaled by 3/5 instead of 5/3, making the larger triangle smaller.
• EI multiplied by 5 and ignored the 3 in the ratio entirely.