According to Official Guinness Records,
This record is for the greatest number of people attending and participating in a mental arithmetic lesson at a single venue.This record is to be attempted by a team of unlimited size.This record is measured by the number of participants.For the purposes of this record, a mental arithmetic lesson must teach the participants the arithmetical calculation skills using only the human brain.
For a complete list of 2018 records, please visit 2018 Guinness Records in India.