NSO Class 3 — Complete Study Notes

Read this straight through — no other book needed

Pattern: Section 1 Logical Reasoning (5Q×1=5) · Section 2 Science (25Q×1=25) · Section 3 Achievers (5Q×2=10) · Total 35Q/40 marks · 60 min · no negative marking.

Each topic below has: a clear explanation → 3 worked examples → a Try It Yourself question (answer given right after, so you can check yourself immediately).

PART A — Logical Reasoning

1. Patterns

A pattern repeats or changes in a fixed, predictable way. To solve it, look at 2–3 items to find the "rule," then apply that rule to find what comes next.

• Example 1: 🔴🔵🔴🔵🔴 __ → Rule: colours alternate → next is 🔵
• Example 2: 2, 4, 6, 8, __ → Rule: add 2 each time → next is 10
• Example 3: A, B, A, B, B, A, B, B, B, __ → Rule: groups of B increase by one each time → next is A

Try It: 3, 6, 9, 12, __? → Answer: 15 (add 3 each time)

2. Analogy and Classification

Analogy = "A is to B as C is to ___," where you must find the same relationship. Classification = grouping items by a shared property and spotting the odd one out.

• Example 1 (analogy): Puppy is to Dog as Kitten is to ___ → Cat (baby-to-adult relationship)
• Example 2 (analogy): Pen is to Write as Scissors is to ___ → Cut (tool-to-action relationship)
• Example 3 (classification): Rose, Lily, Sunflower, Carrot → Carrot is the odd one (it's a vegetable, others are flowers)

Try It: Find the odd one out: Circle, Square, Triangle, Ball → Answer: Ball (it's a 3D object; the rest are flat 2D shapes)

3. Alphabet Test

Know each letter's position: A=1, B=2, C=3 … Z=26. Questions ask what comes before/after, or a fixed number of steps away.

• Example 1: What letter comes right after F? → G
• Example 2: What letter is 3 places after B? → B, C, D, E → E
• Example 3: Which letter is exactly in the middle of A and E? → C (A,B,C,D,E)

Try It: What comes 2 letters before K? → Answer: I (K, J, I — counting backward)

4. Coding-Decoding

A "code" changes each letter using one fixed rule, usually shifting forward or backward through the alphabet by a set number of steps.

• Example 1: If the rule is "+1" (shift forward one), CAT → DBU
• Example 2: Using the same "+1" rule, DOG → EPH
• Example 3: If the rule is "−1" (shift back one), BUS → ATR

Try It: Using the "+1" rule, how is PEN coded? → Answer: QFO (P→Q, E→F, N→O)

5. Ranking Test

Find a position in a line using clues such as "Nth from the left/right" or comparisons like "taller than."

• Example 1: Ravi is 4th from the left in a row of 9 children. His position from the right = 9 − 4 + 1 = 6th.
• Example 2: If Priya is 3rd from the left and 6th from the right, total children = 3 + 6 − 1 = 8.
• Example 3: Amit is taller than Bala. Bala is taller than Chetan. So Amit is the tallest of the three.

Try It: Sana is 5th from the front and 4th from the back in a line. How many children are in the line? → Answer: 5+4−1 = 8

6. Grouping of Figures and Figure Matrix

Grouping sorts shapes by a shared feature (sides, size, shading). A figure matrix is a 3×3 grid where one picture is missing — find the rule across each row and column to fill it in.

• Example 1 (grouping): Group these by number of sides: Triangle, Square, Pentagon, Triangle → two groups: {Triangle, Triangle} and {Square, Pentagon} — or all separately if grouped by exact side-count.
• Example 2 (matrix): Row 1 has 1, 2, 3 dots; Row 2 has 2, 3, 4 dots — the missing 3rd-row pattern should be 3, 4, 5 dots.
• Example 3 (grouping): Group by colour: Red circle, Blue square, Red triangle, Blue star → {Red circle, Red triangle} and {Blue square, Blue star}

Try It: In a matrix where each row's shape gets one extra corner, if row 3 starts with a triangle (3 corners), what comes next in that row? → Answer: a shape with 4 corners, like a square

7. Mirror Images

A mirror image flips a picture left-to-right, like looking in a mirror — it is NOT the same as turning the picture upside down.

• Example 1: The letter "b" appears mirror-flipped as a "d"-shape.
• Example 2: The word "AMBULANCE" is often written backward/mirrored on the front of ambulances so drivers ahead can read it correctly in their rear-view mirror.
• Example 3: A right hand's mirror image looks like a left hand, not another right hand.

Try It: What does the digit "3" look like when mirror-flipped left-to-right? → Answer: it looks like an "E"-ish backward curve — flipped, not rotated

8. Geometrical Shapes

Learn to name shapes and count their sides and corners.

• Example 1: A triangle has 3 sides and 3 corners.
• Example 2: A pentagon has 5 sides and 5 corners.
• Example 3: A circle has 0 sides and 0 corners — it's a curved shape, not a polygon.

Try It: How many sides and corners does a hexagon have? → Answer: 6 sides and 6 corners

9. Embedded Figures

A smaller, simple shape is hidden inside a larger, more complicated drawing. You must find it by carefully tracing lines.

• Example 1: A small square hidden inside the crossing lines of a larger star drawing.
• Example 2: A triangle hidden within the overlapping petals of a flower drawing.
• Example 3: A circle hidden inside the loops of a scribbled line drawing.

Try It: If you're told a rectangle is hidden inside a drawing of overlapping triangles, what should you look for? → Answer: four straight lines meeting at right angles, even if they're formed by the edges of different triangles

10. Days and Dates & Possible Combinations

Days and dates: if you know today's day, you can find any date's day by counting in 7s (since a week always has 7 days). Combinations: counting how many total pairings are possible.

• Example 1: If 1st of a month is a Sunday, then the 8th, 15th, and 22nd are also Sundays (each is 7 days later).
• Example 2: If today is Tuesday, then 10 days from now is Friday (10 ÷ 7 = 1 week + 3 days; Tuesday + 3 = Friday).
• Example 3 (combinations): With 3 shirts and 2 pairs of shorts, total outfits = 3 × 2 = 6.

Try It: With 2 types of ice cream and 3 types of toppings, how many different ice-cream+topping combos are possible? → Answer: 2 × 3 = 6

PART B — Science

1. Plants and Animals

Plants have roots (absorb water/minerals), stems (support + transport), leaves (make food using sunlight), flowers (make seeds), and fruits (protect seeds). Animals are grouped by diet: herbivores (plants only), carnivores (meat only), omnivores (both).

• Example 1: A carrot plant's root is the part we eat.
• Example 2: A lion is a carnivore — it eats other animals.
• Example 3: A bear is an omnivore — it eats both berries (plant) and fish (animal).

Try It: A goat eats only grass and leaves. What type of animal is it? → Answer: Herbivore

2. Birds

Birds have feathers, wings, and beaks shaped for their specific diet.

• Example 1: An eagle has a sharp, hooked beak for tearing meat.
• Example 2: A sparrow has a short, strong beak for cracking seeds.
• Example 3: A hummingbird has a long, thin beak for sipping nectar from flowers.

Try It: What kind of beak would you expect on a bird that eats mainly fish? → Answer: a long, sharp beak good for spearing or gripping slippery fish (like a heron's)

3. Food

Food comes from plants (grains, fruits, vegetables) or animals (milk, eggs, meat) and gives us energy and helps us grow.

• Example 1: Wheat and rice are plant-based staple foods.
• Example 2: Milk and cheese come from animals.
• Example 3: Honey comes from bees, so it's classified as an animal-source food.

Try It: Is an egg a plant-source or animal-source food? → Answer: Animal-source (it comes from a hen)

4. Housing, Clothing and Occupation

Homes and clothes are designed based on the local climate; occupations are matched to specific tools and skills.

• Example 1: People in very cold places (like the Arctic) build homes with thick insulated walls and wear heavy woollen clothing.
• Example 2: People in hot, dry deserts often wear light, loose cotton clothing to stay cool.
• Example 3: A carpenter uses a hammer and saw, while a doctor uses a stethoscope.

Try It: Why might houses in hot regions often have thick mud walls and small windows? → Answer: mud walls and small windows keep the inside cooler by blocking direct heat

5. Transport, Communication and Safety Rules

Transport moves us by land, water, or air. Communication is how we share information (letters, phones, internet). Safety rules keep us safe while traveling.

• Example 1: A train and a bicycle are both land transport.
• Example 2: A submarine is water transport; a helicopter is air transport.
• Example 3: "Always look both ways before crossing the road" is a road safety rule.

Try It: Is a letter or a phone call an example of communication? → Answer: Both are — communication includes any way we share information across distance

6. Human Body

Major organs: heart (pumps blood), lungs (help us breathe), stomach (digests food), brain (controls the body). The five senses: sight, hearing, smell, taste, touch.

• Example 1: The heart pumps blood to every part of the body.
• Example 2: The lungs take in oxygen and release carbon dioxide when we breathe.
• Example 3: Your tongue detects taste, one of the five senses.

Try It: Which organ do you use to smell fresh bread baking? → Answer: The nose

7. Earth and Universe

The Sun is a star that gives light and heat. The Moon has no light of its own — it reflects the Sun's light. Day and night happen because the Earth spins.

• Example 1: We see the Moon glow at night because it reflects sunlight, like a mirror.
• Example 2: It becomes day in your area when the Earth's spin turns your side to face the Sun.
• Example 3: Stars are visible at night mainly because the Sun's brightness doesn't outshine them then.

Try It: Does the Moon make its own light? → Answer: No — it only reflects light from the Sun

8. Matter and Materials

Matter exists as solid (fixed shape), liquid (takes the shape of its container), or gas (spreads to fill any space). Materials include wood, metal, plastic, and glass, each with different properties.

• Example 1: Ice (solid) melts into water (liquid), which can evaporate into water vapour (gas) — all the same substance.
• Example 2: Metal is generally a good conductor of heat; wood is not.
• Example 3: Glass is usually transparent (see-through), while wood is opaque (not see-through).

Try It: What state of matter is the air we breathe? → Answer: Gas

9. Light, Sound and Force

Light comes from sources like the Sun or a bulb. Sound comes from vibrations. A shadow forms when an opaque object blocks light. A force is a push or a pull.

• Example 1: A guitar string vibrating produces sound.
• Example 2: Standing between a lamp and a wall creates your shadow on the wall.
• Example 3: Kicking a ball is an example of applying a push force.

Try It: Is opening a drawer a push or a pull? → Answer: A pull

10. Our Environment

Living things grow, breathe, and reproduce; non-living things do not. Plants, animals, and people depend on each other and their surroundings.

• Example 1: A tree is living (it grows and needs water); a stone is non-living.
• Example 2: Bees depend on flowers for nectar, and flowers depend on bees for pollination — this is an example of living things depending on each other.
• Example 3: Throwing litter in a park harms the environment for both plants and animals living there.

Try It: Is a toy car living or non-living? → Answer: Non-living — it doesn't grow, breathe, or reproduce

PART C — Achievers Section (Higher Order Thinking)

The Achievers Section reuses the 10 Science topics above but asks harder "why," "what if," or "compare" questions instead of plain facts.

• Cause-effect example: "Why does the Moon appear to shine at night?" → Because it reflects the Sun's light (not "the Moon shines," which is just the fact — the "why" is the HOTS version).
• What-if example: "What would happen to a plant kept in a dark cupboard for a week?" → It would struggle to make food and may turn pale/weak, since leaves need light to make food.
• Compare example: "How is a carnivore's set of teeth likely different from a herbivore's?" → A carnivore tends to have sharper, pointed teeth for tearing meat, while a herbivore has flatter teeth for grinding plants.
• Multi-step example: "Why do wet clothes dry faster on a sunny, windy day than on a cloudy, still day?" → Combines two facts: heat speeds up evaporation (Matter topic) and wind carries away water vapour faster (Environment topic).

Practice this yourself: for every fact you learn in Part B, ask "why does this happen?" or "what would change if this were different?" — that single habit is the best Achievers-section preparation there is.

Once you've read through a topic here, try the matching questions in the NSO Class 3 mock exam and practice quiz built earlier in this conversation.