Skip over navigation
Cambridge University Faculty of Mathematics NRich logo
menu search
  • Teachers expand_more
    • Early years
    • Primary
    • Secondary
    • Post-16
    • Events
    • Professional development
  • Students expand_more
    • Primary
    • Secondary
    • Post-16
  • Parents expand_more
    • Early Years
    • Primary
    • Secondary
    • Post-16
  • Problem-Solving Schools
  • About NRICH expand_more
    • About us
    • Impact stories
    • Support us
    • Our funders
    • Contact us
  • search

Or search by topic

Number and algebra

  • The Number System and Place Value
  • Calculations and Numerical Methods
  • Fractions, Decimals, Percentages, Ratio and Proportion
  • Properties of Numbers
  • Patterns, Sequences and Structure
  • Algebraic expressions, equations and formulae
  • Coordinates, Functions and Graphs

Geometry and measure

  • Angles, Polygons, and Geometrical Proof
  • 3D Geometry, Shape and Space
  • Measuring and calculating with units
  • Transformations and constructions
  • Pythagoras and Trigonometry
  • Vectors and Matrices

Probability and statistics

  • Handling, Processing and Representing Data
  • Probability

Working mathematically

  • Thinking mathematically
  • Developing positive attitudes
  • Cross-curricular contexts

Advanced mathematics

  • Decision Mathematics and Combinatorics
  • Advanced Probability and Statistics
  • Mechanics
  • Calculus

For younger learners

  • Early Years Foundation Stage

Reaction Timer Timer

Age 16 to 18
Challenge Level Yellow star
  • Problem
  • Getting Started
  • Student Solutions
  • Teachers' Resources

The timer gives us our reaction time, but tells us nothing about the random process it implements. One way to find how long the shape disappears for would be to use a stopwatch and click after a known interval. Provided this interval is big enough, subtracting the reaction time will give us the time from the shape's disappearence to its reappearance.

Carry this out a number of times and plot your data. What does the distribution look like? Does your experimental evidence support a conjecture for how the random process works?


Alexander from Wesley College thinks that he observed a difference between the reflexes for left and right hands. We wonder if this could be used to test people who claim to be ambidextrous?

I think that beause I'm right handed, when the star appeared or the moon I found I had an instant reflex. But when I used my left hand I had to think about it because I'm right handed. All up its about reflex.


You may also like

Very Old Man

Is the age of this very old man statistically believable?

Chi-squared Faker

How would you massage the data in this Chi-squared test to both accept and reject the hypothesis?

Chance of That

What's the chance of a pair of lists of numbers having sample correlation exactly equal to zero?

  • Tech help
  • Accessibility Statement
  • Sign up to our newsletter
  • Twitter X logo

The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to embed rich mathematical tasks into everyday classroom practice.

NRICH is part of the family of activities in the Millennium Mathematics Project.

University of Cambridge logo NRICH logo