A student performs an experiment of measuring the thickness of a slab with a vernier calliper whose \(50\) divisions of the vernier scale are equal to \(49\) divisions of the main scale. He noted that zero of the vernier scale is between \(7.00\; cm\) and \(7.05 \;cm\) mark of the main scale and \(23^rd\) division of the vernier scale exactly coincides with the main scale. The measured value of the thickness of the given slab using the calliper will be

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.