ROUND 01 / 03

Life expectancy around the world

World · 1960–2023Years

Year

Your scale

How to play

Three graphs every day. Find the missing scale.

A new set arrives at midnight UTC in each mode. Past days become archives, and your progress is saved on this browser.

  1. Guess the minimum and maximum

    Enter the lowest and highest values reached by the line. All scales are linear.

    In Stocks, one value is given. For a constant graph, both values are equal.

  2. Lock in and compare

    Correct shows the real scale. Your guess shows your scale. Compare the axis numbers—the line’s shape stays the same.

  3. See how close you were

    Earn up to 100 points. More overlap between your range and the correct range means a higher score.

Derivative Mode

Guess the range of the line’s rate of change instead. The toggle stays on between rounds.

− Decreasing0 No change+ Increasing

Math uses exact derivatives. For measured data, each point is the average change between observations; the connecting line is a visual guide. Stocks use change per trading session.

After locking a guess, the toggle is available again in the next round.