7 mistakes learners make with ordering and logic, each one named and explained.
Write the chain out in order before answering anything about it.
All Zibs are Trins becomes all Trins are Zibs.
The sentence contains the same words both ways round, so the reverse feels like the same fact.
Question. All Zibs are Gloops. All Gloops are Trins. What must be true?
A common answer. All Trins are Zibs
The answer. All Zibs are Trins
Why. Every Zib is inside Gloops, and every Gloop is inside Trins, so every Zib is a Trin. Nothing says every Trin is a Zib; the arrow only points one way.
An all statement points one way. Never turn it round for free.
Aisha is given red when the clue says Aisha does not like red.
With several clues in play, the first one read fades by the time the answer is chosen.
Question. Aisha does not like red or blue. Ben likes green. Which colour is Aisha's?
A common answer. Red
The answer. Yellow
Why. Red and blue are ruled out for Aisha by her own clue, and green is taken by Ben. Only yellow is left standing.
Check your answer against each clue, one by one, before moving on.
Cannot tell is chosen when combining the clues settles it.
Each clue on its own really is not enough, and the step of joining them is the easy one to miss.
Question. The red box does not hold apples. The blue box holds plums. What is in the red box?
A common answer. Cannot tell
The answer. Pears
Why. The red box cannot hold apples by its own clue, and it cannot hold plums because the blue box has them. Only pears are left, so the clues together do tell.
When one clue is not enough, put it next to the other clues before saying cannot tell.
Some sheep have patches becomes the animal must be a cow.
A confident answer feels better than a careful one, even when the clues stop short of proof.
Question. All cows have patches. Some sheep have patches. An animal has patches. What is it?
A common answer. It must be a cow
The answer. It is either a sheep or a cow
Why. Patches do not belong only to cows here, because some sheep have them too. The clues allow both, so certainty is not available.
Only say must when the clues rule out every other possibility.
The answer given is that it cannot be worked out, when the statements do settle it.
The two statements never compare the first and last people directly.
Question. Tom > Sam and Sam > Ben, who is shortest
A common answer. cannot tell
The answer. Ben
Why. If Tom is above Sam and Sam is above Ben, the whole order is fixed.
Link the statements through the name they share. That is usually enough to fix everything.
The person in the middle of the chain is given for a question about either end.
The middle name appears in both statements, so it is the one that stands out.
Question. Tom > Sam > Ben, who is shortest
A common answer. Sam
The answer. Ben
Why. Sam is taller than Ben, so Sam is not the shortest.
The answer to an extreme question is always at an end, and ends appear only once.
The tallest is given when the shortest was asked for.
The chain has been built correctly and only the last reading of it is inverted.
Question. Tom is taller than Sam, Sam is taller than Ben. Who is shortest?
A common answer. Tom
The answer. Ben
Why. Tom is at the tall end of the chain, so he cannot be the shortest.
Write the names in a line, tallest first. Then read from whichever end the question wants.
WAJD spots these patterns in your child's answers and names the one behind their wrong answers, instead of just marking them wrong.