Significant Figures NEET Notes: Rules, Tricks, Examples & Practice Questions

 - Dr.Sanjaykumar Pawar 

Significant Figures and Measurement Errors | NEET Smart Notes

NEET Smart Notes: Significant Figures Rules, Calculation Tricks and Quick Revision Guide

Internal Links

Units and Dimensions NEET Notes

→ /units-and-dimensions-neet-notes

Measurement Errors and Accuracy NEET Notes

→ /measurement-errors-neet-notes

Scientific Notation and Powers of Ten

→ /scientific-notation-neet-notes

Important Class 11 Physics Formula Notes

→ /class-11-physics-formula-notes

NCERT Chemistry Chapter 1 Some Basic Concepts of Chemistry Notes

→ /some-basic-concepts-of-chemistry-neet-notes

NEET Physics Numerical Problems with Solutions

→ /neet-physics-numericals

NEET Chemistry Revision Notes PDF

→ /neet-chemistry-revision-notes

NEET Smart Notes: Significant Figures & Mass Calculation

Part 1: Question and Answer

Question:

The mass of a box measured by a grocer’s balance is 2.30 kg. Two gold pieces of masses 20.15 g and 20.17 g are added to the box. Find:

(a) The total mass of the box.
(b) The difference in the masses of the pieces to correct significant figures.

Solution:

Given:

• Mass of box = 2.30 kg
• Mass of gold piece 1 = 20.15 g
• Mass of gold piece 2 = 20.17 g

Step 1: Convert kg into grams

1 kg = 1000 g

2.30 kg = 2.30 × 1000 = 2300 g

(a) Total Mass of Box

Mass of gold pieces:

20.15 g + 20.17 g = 40.32 g

Total mass:

2300 g + 40.32 g = 2340.32 g

For addition, answer should have the same decimal places as the least precise value.

2340.32 g ≈ 2340 g

Final Answer (a): 2.34 kg

(b) Difference in Masses

20.17 g - 20.15 g = 0.02 g

Final Answer (b): 0.02 g

Part 2: Short Notes

Significant Figures

Significant figures are the meaningful digits present in a measurement. They indicate the accuracy and precision of a measurement.

Example:
2.30 kg has 3 significant figures.

Rules for Addition and Subtraction

In addition and subtraction, the number of decimal places decides the final answer.

Addition/Subtraction → Check Decimal Places

Example:
20.15 + 20.17 = 40.32

Unit Conversion

Before calculation, all quantities must be converted into the same unit.

1 kg = 1000 g

Steps to Solve Questions

1. Convert all quantities into the same unit.
2. Perform addition or subtraction.
3. Apply significant figure rules.
4. Write final answer with correct unit.

Part 3: Concept Table

Concept	Meaning	Example
Measurement	Finding the value of a physical quantity	Mass = 2.30 kg
Significant Figures	Meaningful digits in measurement	2.30 has 3 SF
Addition/Subtraction Rule	Decimal places decide answer	20.15 + 20.17
Unit Conversion	Change units before calculation	1 kg = 1000 g

Part 4: Memory Mnemonics

Mnemonic 1:

"ADD-SUB → Decimal Dekho"

Addition and subtraction में हमेशा decimal places count करो.

Mnemonic 2:

"MULTI-DIV → Significant Gino"

Multiplication and division में significant figures count करो.

Mnemonic 3: Zero Rule

"Between and Behind = Important, Before = Ignore"

• Between zeros → Significant
• Decimal के बाद ending zeros → Significant
• Starting zeros → Not significant

30-Second Revision Box

SIGNIFICANT FIGURES

Addition/Subtraction
        ↓
Decimal Places

Multiplication/Division
        ↓
Significant Figures

Zero Rules:
Between digits → Significant
After decimal → Significant
Before first digit → Not Significant

1 kg = 1000 g

Convert units before calculation.