Deduce #78: Trick-or-treat — the solution

The Deduce puzzle from October 31, 2026, worked through clue by clue: 7 clues, 3 rounds of crossing off, and no guessing anywhere.

The puzzle

Four people — Becca, Darla, Wendy and Rhett — and three things to work out about each: their costume, trading and time. The clues only ever rule things out.

1. Becca is not the one dressed as a mummy.
2. The one dressed as a dinosaur is exactly 2 hours after Wendy.
3. The one trading away the gum is not the one out at 7pm.
4. Becca is the one trading away the lollipops.
5. The one dressed as a vampire is exactly 2 hours after Becca.
6. Rhett is the one out at 8pm.
7. The one trading away the taffy is exactly 3 hours after Wendy.

The walkthrough

A round is one pass over the clues. Each round applies what the last one settled; every step below is an elimination the clues force, in the order a solver would take them.

Round 1

Start with every possibility open, and take the clues in order.

Clue 1, “Becca is not the one dressed as a mummy”: mummy comes off Becca.

Clue 2, “The one dressed as a dinosaur is exactly 2 hours after Wendy”: dinosaur comes off Wendy; 7pm and 8pm come off Wendy.

Clue 4, “Becca is the one trading away the lollipops”: lollipops comes off Darla, Wendy and Rhett. That settles it: Becca’s trading is lollipops.

Clue 5, “The one dressed as a vampire is exactly 2 hours after Becca”: vampire comes off Becca and Wendy; 7pm and 8pm come off Becca.

Clue 6, “Rhett is the one out at 8pm”: 8pm comes off Darla. That settles it: Rhett is out at 8pm.

Clue 7, “The one trading away the taffy is exactly 3 hours after Wendy”: taffy comes off Darla and Wendy; 6pm comes off Wendy. That settles it: Wendy is out at 5pm.

Round 2

Go back over the clues with the new facts in hand.

Nobody but Rhett can still have taffy, so Rhett’s trading is taffy.

5pm is Wendy’s, so it comes off Becca and Darla. That settles it: Becca is out at 6pm.

Nobody but Darla can still have 7pm, so Darla is out at 7pm.

Clue 2, “The one dressed as a dinosaur is exactly 2 hours after Wendy”: dinosaur comes off Becca and Rhett. That settles it: Becca’s costume is ghost.

Clue 3, “The one trading away the gum is not the one out at 7pm”: gum comes off Darla. That settles it: Darla’s trading is pretzels.

Clue 5, “The one dressed as a vampire is exactly 2 hours after Becca”: vampire comes off Darla.

Round 3

Go back over the clues with the new facts in hand.

Ghost is Becca’s, so it comes off Darla, Wendy and Rhett. That settles it: Wendy’s costume is mummy.

Mummy is Wendy’s, so it comes off Darla and Rhett. That settles it: Darla’s costume is dinosaur and Rhett’s costume is vampire.

Pretzels is Darla’s, so it comes off Wendy. That settles it: Wendy’s trading is gum.

The answer

Previous: Deduce #77 (Fri, Oct 30) · Next: Deduce #79 (Sun, Nov 1) · All Deduce solutions

About Deduce

Deduce is Noggin’s daily logic grid: four people, three things to work out about each, and clues that never hand you an answer. Every puzzle has exactly one solution and can be finished by crossing off alone. How to play Deduce, or play today’s.