The abacus system of mental calculation is a system where users mentally visualize an abacus to do calculations. No physical abacus is used; only the answers are written down. Calculations can be made at great speed in this way. For example, in the Flash Anzan event at the All Japan Soroban Championship, champion Takeo Sasano was able to add fifteen three-digit numbers in just 1.7 seconds.
This system is being propagated in China, Singapore, South Korea, Thailand, Malaysia, Japan and India. Mental calculation is said to improve mental capability, increases speed of response, memory power, and concentration power.
Many veteran and prolific abacus users in China, Japan, South Korea, and others who use the abacus daily, naturally tend to not use the abacus anymore but perform calculations by visualizing the abacus. This was verified when the right brain measured heightened EEG activity when calculating and compared with non-veterans who were using the abacus to perform calculations.
The standard abacus can be used to perform addition, subtraction, division, and multiplication; the abacus can also be used to extract square-roots and cubic roots. Universal Concept of Mental Arithmetic System (UCMAS), a brain development programme, is implemented from KG1 to Grade 8.  The UCMAS International Competition What started as a mere vision more than 20 years ago is now a reality with thousand of learners from over 50 countries competing in this international competition every year.  22nd 2017 Annual UCMAS National and International Abacus and Mental Arithmetic Competition 19th Nov 2017 (National Competition, Malaysia) and 9th & 10th Dec 2017 (International Competition in Bali, Indonesia).
- "Research on the benefits of mental abacus for development". Retrieved March 12, 2012.
- Alex Bellos (2012), "World's fastest number game wows spectators and scientists", The Guardian
- "(Chinese)Teaching Kids Visit to use abacus for mental calculation". Retrieved March 12, 2012.
- Universal Concept of Mental Arithmetic System (UCMAS), a brain development programme, is implemented from KG1 to Grade 8.
- Ku Y, Hong B, Zhou W, Bodner M, Zhou YD (2012). "Sequential neural processes in abacus mental addition: an EEG and FMRI case study". PLoS ONE. 7: e36410. PMC . PMID 22574155. doi:10.1371/journal.pone.0036410.
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