Stack

Stack asks how many of an everyday object would match the height of a landmark. You build the answer by dragging a stack up or down, with no ruler and no number pad.

How it works

Each round pairs an object, like a banana or a credit card, with something big, like the Eiffel Tower or Mount Everest. Drag up on the stack to add objects and down to remove them; the further you drag, the faster it grows. The + and − buttons fine-tune, and ×2 and ÷2 make big jumps.

When the stack fills the space the view zooms out, and the landmark card is never drawn to scale, so you have to estimate rather than line things up.

Scoring

Exactly right scores 100. Being twice too many or half too few scores 50, and four times off scores nothing. Because it's based on ratios, being 10% off a million is scored the same as being 10% off ten.

Sources

Every landmark height comes from its Wikipedia article and every object size from the standard that defines it, such as the ISO credit card standard or the US Mint's coin specifications. Both are shown after each round.

Example

How many bananas tall is the Statue of Liberty? It's 93 m from the ground to the torch, and a medium banana is about 19 cm long, so the answer is about 489 bananas. A guess of 300 would be 1.6 times too few and score 65.

Tips

1Convert both things to a unit you can picture, like metres or storeys.
2A storey of a building is about 3 m. An adult is about 1.7 m.
3Use ×2 and ÷2 to get the order of magnitude right first, then fine-tune.