The invention "Trio-meter"is a multipurpose instrument by using- "Multi-slotted link sliding assembly mechanism" - for triangle solutions including 'Pythagoras theorem' as a ready reckoner (Fig.II). Useful instrument with marker block attachment to draw and measure straight lines, lengths, arcs, semi circles, circles, bicircles, tricircles, parallelograms, rhombuses, trapezoids, parallel lines and triangles with fractional and accurate measurements easily and quickly (Fig. Ill to VIII). The novel instrument with trisector attachments, trisects an angle and multiplies an angle into double, triple & quadruple as well as reduces an angle in to two-third^ half, one third and quarter fractionally and accurately (Fig. IX). It comprises three slotted links with in-built main measuring scales, which are also working as sides of a triangle, three vernier calipers with three protractors and three indicators, assembled by centre pins, with all necessary attachments, parts and components (1 to 99) for complete operations and perfect functioning.