IT may be the electronic age but an instrument that has been around for thousands of years is making a comeback in Singapore and Malaysia. The abacus is being introduced in government schools in both countries to give pupils a visual image of mathematics, which the electronic equivalent does not provide. A teacher at a Singapore private school, which began using the abacus last year, said that after students had been taught to visualise numbers with the beads ''they can work out sums without using an electronic calculator''. Singapore's Education Ministry said it would supply abacuses to Primary Three pupils in selected schools in a pilot project to set the stage for the instrument's more widespread use. Educational experts say the abacus can increase significantly students' understanding of mathematical concepts and their performance in mental calculations. The ministry said the abacus lessons would supplement existing techniques for teaching mathematics. The Primary Three pupils would begin by learning simple calculations with the abacus. It said the use of the abacus would enhance their ability to calculate, which was ''fundamental in the primary mathematics curriculum''. The Singapore move follows an announcement by the Malaysian Minister of Education, Datuk Amar Dr Sulaiman Daud that more than 7,000 teachers would be trained to use the abacus this year so it could be introduced as a teaching aid in mathematics in primary schools. Dr Sulaiman said users of the abacus would develop both manual and mental skills because their fingers would have to be dexterous and their minds able to remember the formula for moving the beads.