Which of the following topics are not part of primary school Mathematics curriculum as per NCF 2005 ?

The correct answer is Ratio.

According to the National Curriculum Framework (NCF) 2005, the primary school mathematics curriculum focuses on developing children's spatial reasoning, visualization, number sense, and pattern recognition capabilities through concrete and joyful learning experiences.

Key topics included in the primary mathematics curriculum (Classes I–V) as per NCF 2005 are:

1. Tessellation: Helps children understand spatial concepts, shapes, tiling, and geometry without formal definitions.
2. Symmetry: Fosters visual and spatial understanding of objects and shapes.
3. Patterns: Essential for developing algebraic thinking, sequence identification, and mathematical logic at an early stage.
4. Data Handling, Measurement, and Shapes (Geometry): Introduced through hands-on activities.

Why "Ratio" is not part of the primary school curriculum:
The concept of Ratio involves abstract proportional thinking and multiplicative reasoning, which require a higher level of cognitive development. Therefore, as per NCF 2005, topics like Ratio, Proportions, Algebra, and Percentages are introduced at the upper primary stage (Classes VI–VIII) rather than the primary stage.