Original revision introduction and starter practice. Full learning texts are available through the publisher links below. This guide is not a CBSE-issued solution manual.
Revision introduction
Measurement requires a defined quantity, unit and instrument. Instrument resolution limits the precision of a reading. Repeated measurements help identify random variation; calibration helps detect systematic errors. Write the value with its unit and appropriate significant figures. This is an optional extension to standard Science.
Curriculum navigation
Measurement
Understanding Motion through Experience
Newton’s Laws of Motion
Advanced Simple Machines
Work and Energy
Structure of Atom
Chemical Bonding
Mixtures and Separation
Microscope and Microscopy
Biotechnology
Consult the current official syllabus for examinable sections, project-only content, practicals, prescribed texts and exclusions. A unit index does not override those boundaries.
Original practice
Which action best reduces random variation in a measured result?
Repeat and average measurements
Remove all units
Always round to an integer
Use an uncalibrated instrument
Worked answer
Repeat and average measurements
Averaging repeated observations reduces the effect of random variation; it does not remove systematic error.
Full publisher materials and answer resources
CBSE 9 Science at Advanced Level (optional) · syllabus · CBSE · 2026-27 The current official syllabus defines examinable content, internal assessment, practicals and prescribed books. Unit names in the app are a navigation index; consult this document for exclusions and assessment boundaries.
DIKSHA · curriculum learning resources · Ministry of Education / DIKSHA · Current portal Choose CBSE/NCERT, Class 9, subject and medium. This is a searchable portal, not a promise of a specific playable lesson.