Why there is a need of rounding off figures during calculation?

Short/Brief Note

When performing calculations with measured quantities, the rule is that the accuracy of the final result is limited to the accuracy of the least accurate measurement.
In other words, the final result cannot be more accurate than the least accurate number involved in the calculation.
Sometimes, the final result of a calculation often contains figures that are not significant.
When this occurs, the final result is rounded off.

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Chapter 2: Introduction to Analytical Chemistry - Exercises [Page 23]

Chapter 2 Introduction to Analytical Chemistry
Exercises | Q 2. (I) | Page 23

Choose the correct option:

The number of significant figures in 1.50 × 10⁴ g is __________

Choose the correct option:

In Avogadro’s constant 6.022 × 10²³ mol^-1, the number of significant figures is ________

State the rules for deciding significant figures.

Solve the following question:

Round off the following quantity to two significant figures:

0.00254 m

Solve the following question:

Round off the following quantity to two significant figures:

1.491 × 10⁵ mg

Solve the following question:

Round off the following quantity to two significant figures:

199 g

Solve the following question:

Round off the following quantity to three significant figures:

643 cm²

Solve the following question:

Round off the following quantity to three significant figures:

0.039 m

Solve the following question:

Round off the following quantity to three significant figures:

649.85

Express the following sum to the appropriate number of significant figures:

2.3 × 10³ mL + 4.22 × 10⁴mL + 9.04 × 10³ mL + 8.71 × 10⁵ mL