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

Planet Plex Time

Age 5 to 7
Challenge Level Yellow star
  • Problem
  • Getting Started
  • Student Solutions
  • Teachers' Resources

Planet Plex Time


On Planet Plex, there are only six hours in a day but the days of the week are the same as ours. Arog the alien lives on Planet Plex.

Here is a clock which shows how Arog spends each hour of the day during the week:

between 0 and 1 o'clock - gets up; 1-2 o'clock - school; 2-3 o'clock - lunch time; 3-4 o'clock - play; 4-5 o'clock - dinner and 5-6 o'clock - sleeping.

What time does school start?

Arog starts his dinner at $4$ o'clock. What will he be about to do two hours later? What was he about to do five hours earlier?

Arog gets into bed on Wednesday evening. How long is it until school finishes on Friday?


Why do this problem?

This simple problem focuses on duration and will encourage learners to consider the passing of time in a different context.

Key questions

Can you show me on the clock what time school starts?
Could you use the clock to count how many hours have passed?

Possible extension

Children could have a go at the problem Times of Day.

You may also like

How Many Days?

How many days are there between February 25th 2000 and March 11th?

On What Day Did it Happen?

Read this article to find out the mathematical method for working out what day of the week each particular date fell on back as far as 1700.

Calendars

Calendars were one of the earliest calculating devices developed by civilizations. Find out about the Mayan calendar in this article.

  • 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