The Junior Mental Calculation World Championship 2024 will take place in September 2024 in Bielefeld 🇩🇪.
The official website of the JMCWC has the official information about the program, and contact details in case you have any questions about the competition. 📧
This page contains various resources for participants, so that you can prepare effectively. It was updated on 06 September 2023 and will be updated again before the 2024 competition. I hope it will help you! 😊
Changes in the 2023 Competition
The “Currency” page has been completely changed, but it still tests the same skills of approximate multiplication and division. A typical question will give an exchange rate [e.g. 1 USD (US dollar) = 5.3286 BRL (Brazilian real)] and ask you to convert some amounts using this figure [e.g. 12.34 USD into BRL, or 34.03 BRL into USD]. All answers are given rounded to 2 decimal places. So 34.03 ÷ 5.3286 would be 6.39, when rounded suitably. Please refer to the Simulator below for details.
Some pages have a slightly greater maximum difficulty.
There are about 6 pages of Surprises, and these are scattered throughout the paper, as in 2022.
Participants should be aware of how “variables” work in mathematics. For example, 10x + 3 means that whatever value x represents, you multiply it by 10, and then add 3. So, if x = 5, then 10x + 3 would equal 5 × 10 + 3 = 53.
JMCWC Simulator
The exam contains 20+ pages of standard questions, plus a few pages of Surprises.
George Lane has produced a simulator of the standard questions for 2023, which you can download here to see what the exam will look like. You will need Excel, or an open-source alternative such as LibreOffice.
- Simulator for Juniors 1 (ages up to 11 years)
- Simulator for Juniors 2 (ages 12–14 years)
- Simulator for Seniors (ages 15+ years)
The Surprises use similar skills, but they are not in any simulator, because they are a surprise 😉
Instructions for Simulator
The simulators randomly regenerate new questions every time you open or edit the file. The answers are written in white, and you can reveal them simply by changing the answer column to your choice of colour, for example red.
Be caseful not to edit or close the file between solving the questions and revealing the answers, otherwise you won’t be able to check them! On LibreOffice, changing the colour also regenerates all the questions, which is unhelpful. However, you can turn off auto-calculation to avoid this problem.
The print ranges are already set. but they can still be checked before printing. If anything looks bad, just go to Page Layout & Margins, and set the page to print on 1 tall by 1 wide.
As an alternative to printing, you can simply write the answers on paper and then check them against the answers in the document.
General Advice
Generally, it is recommended that participants start at the beginning of the paper and work through systematically. However, most participants will not finish the paper, so it may be a good strategy to skip questions or sections that you find difficult, so you have time for your favourite types of question and Surprises.
It is strictly forbidden to write any method or intermediate calculations anywhere during the test. All calculation must be done mentally, and only the answers may be written.
Mental Calculation Techniques & Training Tools
Some of the categories are best solved using advanced techniques, that you might not learn at school! Here are some resources and tools for the most difficult categories. Many participants in the competition will only know the basics—they won’t know most of these extra methods!
Calendar Dates
- Human Calendar Algorithm: the fastest human calendars use a variation of this method.
- Online Training Tool: this was developed by Katie Kermode—a world record-holder at memory sports.
Multiplication
- Cross-Multiplication Method: how to multiply large numbers like 3772 × 2843 = 10723796
Division
- Cross-Division Method: how to divide by large numbers like 2843
Fractions
- Fraction Addition and Subtraction: Mathematics and algorithm
- Fraction Multiplication and Division: Mathematics and algorithm
Square Roots & Deep Roots
- Estimating Square Roots: fast method to get 3–5 digits of accuracy on inexact square roots.
- Estimating Deep Roots: fast method to get 2–3 digits of accuracy on inexact cube roots and deeper roots.
- Mental Square Roots Method: accurate method for obtaining as many decimal places as you like.
Sums of Squares
- Online Training Tool: makes practice more efficient, as it checks your answer automatically. Sums of squares questions typically have multiple possible correct answers!
Good luck—see you in Bielefeld! 🎉