A Mental Maths Game for Kids

Rigid Digit is a free daily maths puzzle for kids aged 8 and up, and for the grown-ups trying to keep up with them. Each day there's a target number and five numbers to make it from, using +, −, × and ÷. Steve made it with his daughter Tui, who's 9, so it's been kid-tested from the very first puzzle.

What It Practises

It doesn't feel like homework, but every puzzle is real mental arithmetic:

• Estimating. Every move starts with a guess: if I multiply these two, will I land near the target? Kids get quicker at ballparking an answer, and at spotting when one can't be right. A calculator can't do that part for you, and it's the skill we've noticed improve most from playing.
• Number facts. Times tables, halves and doubles, and adding up to tens and hundreds, all used for a reason instead of drilled.
• Thinking ahead. A solution can take up to four steps, so you learn to plan a move or two in advance, and to work backwards from the target.
• Sticking with it. Every puzzle is checked before it's published, so there's always an answer and a tricky one is worth another go. There's no clock counting down, either, so there's no panic.

Where to Start

Start on Easy. The target is always under 100, and three or four of the five numbers are always enough. Hints walk first-timers through their first few moves. When Easy gets too easy, move up to Medium, which has three-digit targets like Countdown on TV. Hard and Extreme use all five numbers and will stretch most adults.

Want a few strategies to start with? Have a look at our mental maths tips.

Better Together

Everyone gets the same puzzles each day, so a kid and a parent (or a grandparent) can each solve one, then compare how they got there. Easy, Medium and Hard usually have more than one route to the answer, which makes for a good chat over breakfast.

Fair warning: kids get fast. Here's what Tui sent the family one morning.

In the Classroom

Rigid Digit is free, with no ads and no sign-up, so there's nothing for a school to set up. It runs in any web browser, on a phone, tablet, laptop or Chromebook.

A new set of puzzles arrives every day, so it makes a quick warm-up: put Easy up on the big screen and solve it as a class, then let kids try Medium on their own.

Tui's school shared it with families ahead of their Mathathon fundraiser, and we wrote about why it's such a good fit.