Each symbol stands for a different digit, and no two symbols share one. What digit does the asked symbol stand for?

Leading symbols are not zero. Which digit is ●?

On this island every person either always tells the truth or always lies. Lena says: “Aiko and Mara are both truth-tellers.” Mara says: “Aiko and Lena are both truth-tellers.” Aiko says: “Lena is a liar.” Tomas says: “Aiko and Mara are both truth-tellers.” How many of them are liars?

Which figure does not belong with the others?

Gear 1 turns clockwise (↻). Which way does the last gear turn?

Numbers show each gear's tooth count. Gear 1 drives the chain.

A is to B as C is to — which option?

Start on the marked square and obey each square's instruction, moving that many squares in that direction. How many moves does it take to land on the target?

Tinted square = start · ◎ = target. Each square's arrow and number is one move.

Kofi is 3 times as old as Lena. In 3 years' time, Kofi will be 2 times as old as Lena. How old is Kofi now?

Every shape of the same kind weighs the same. Using the balanced scales, how many shapes are needed to balance the last one?

Every scale is balanced. How many ◆ balance the shapes on the last scale?

Which piece completes the pattern?

How many rectangles does the figure contain, counting every size?

What comes next in the series?

Kofi is slower than Dana. Tomas is slower than Omar. Dana is faster than Tomas. Omar is slower than Kofi. Who is the second fastest?

How many cubes are in this stack, counting the ones you cannot see?

Which figure continues the series?

Which option shows the same figure rotated (not flipped)?

What comes next in the series?

In a certain code, STONE is written as PQLKB. How is VALLEY written in the same code?

Each box always applies the same hidden rule, shown by its worked examples. What comes out of the pipeline?