Study guides › Level 9 · If–Then

Only if

Level 9 · for questions like “Sam rides the train only if Sam has a ticket.”

💡 The idea

“A only if B” means A never happens without B. So if A happens, B happened too.

🪜 The steps

1. A happened → B happened.
2. B didn’t happen → A didn’t happen.
3. B happened → we can’t tell about A (a ticket doesn’t make you ride).

⚠️ Watch out

• “Only if” is not the same as “if”: having a ticket doesn’t mean you rode.

🎯 Try these

1. A plant grows only if it gets water. This plant got water. Did it grow?

Answers: 1) Can’t tell

This guide is also in the 10LogicQ app: tap “📖 Study guide” after a puzzle.