Chapter 7 of 14
⬅️ Ch 6: Fun with Give and Take Ch 8: Who Is Heavier? ➡️
NCERT Class 3 Mathematics • Classic CBSE Track

Chapter 7: Time Goes on...

Seconds, Minutes, Hours, Days, Months, Years, Timeline & Age Problems | CBSE Session 2026–27

Core Pedagogical Competencies & Concepts
  • Categorizing events by duration: taking seconds, minutes, hours, days, months, or years.
  • Reading dates and understanding different date notations (DD/MM/YYYY).
  • Building a personal life timeline: chronological ordering of milestone events.
  • Calculating age difference between family members.
Personal Milestone Timeline — Chronological Ordering Born Age 0 First Steps Age 1 Joined School Age 4 Class 3 Now Age 8 A timeline arranges historical events in the exact order they occurred.

All Textbook Exercises & In-Text Tasks (17 Questions)

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Q1 Time Duration Estimation • Categorization
Classify each activity into 'Seconds', 'Minutes', 'Hours', or 'Days': (a) To blink your eyes, (b) To knit a woollen sweater, (c) To boil a cup of milk, (d) For curd to set from warm milk.
[2 Marks]
✅ Step-by-Step Solution & Working
Classifications:
• (a) Blink your eyes: Seconds (fraction of a second)
• (b) Knit a sweater: Days (usually several days or weeks)
• (c) Boil a cup of milk: Minutes (approx 3 to 5 minutes)
• (d) For curd to set: Hours (approx 6 to 8 hours).
CBSE Step-by-Step Marking Scheme
Correct duration category for all 4 activities 2.0 M
Q2 Birth Certificate Analysis • Date Calculations
Look at Bincy's birth certificate: Date of birth: 02/05/2018 (2 May 2018). (a) How old was Bincy on 2 May 2026? (b) In which year did she celebrate her 5th birthday?
[2 Marks]
✅ Step-by-Step Solution & Working
Analysis:
• (a) Age on 2 May 2026:
2026 - 2018 = 8 years old.
• (b) 5th Birthday Year:
2018 + 5 = 2023 (on 2 May 2023).
CBSE Step-by-Step Marking Scheme
Correct subtraction for age (8 years) 1.0 M
Correct year calculation for 5th birthday (2023) 1.0 M
Q3 Age Difference Word Problem
Rohan's mother is 34 years old. His grandmother is 62 years old. (a) What is the age difference between Rohan's mother and grandmother? (b) If Rohan is 8 years old, by how many years is his mother older than him?
[2 Marks]
✅ Step-by-Step Solution & Working
Calculations:
• (a) Mother & Grandmother:
62 - 34 = 28 years.
• (b) Mother & Rohan:
34 - 8 = 26 years.
CBSE Step-by-Step Marking Scheme
Correct subtraction for grandmother & mother (28 years) 1.0 M
Correct subtraction for mother & Rohan (26 years) 1.0 M
Q4 Ultat-Pulta Story • Absurd Time Units Correction
Correct the ridiculous time words in this funny story:
'As the sun rises in the evening, Sumana wakes up. She washes her face quickly in 2 hours and runs out to the pond. She takes 10 months to reach the pond and catches a fish in 2 days.'
Rewrite the story with sensible time units (seconds, minutes, morning, hours).
[3 Marks]
✅ Step-by-Step Solution & Working
Corrected Sensible Story:
• 'As the sun rises in the morning (not evening), Sumana wakes up. She washes her face quickly in 2 minutes (not 2 hours) and runs out to the pond. She takes 10 minutes (not 10 months) to reach the pond and catches a fish in 2 minutes/seconds (not 2 days).'
CBSE Step-by-Step Marking Scheme
Corrected morning for sunrise 1.0 M
Corrected minutes for washing face and walking 1.0 M
Sensible duration for catching fish 1.0 M
Q5 Calendar Magic • 3x3 Magic Square Sum
On any standard monthly calendar page, draw a 3x3 square covering 9 dates.
(a) If the date in the exact center of the 3x3 box is 14, what is the sum of all 9 dates in the box?
(b) Explain the quick trick to find this sum in 2 seconds.
[3 Marks]
✅ Step-by-Step Solution & Working
Step-by-Step Calendar Magic:
(a) Sum of 9 Dates:
• Quick Magic Formula: Center Number × 9.
• Center number = 14.
• Sum = 14 × 9 = 126.

(b) The Trick Explained:
• On a calendar, the numbers symmetrically surround the center number (e.g., 14-8 and 14+8, 14-7 and 14+7, 14-1 and 14+1).
• The average of all 9 numbers is exactly the center number. Therefore, simply multiplying the center date by 9 gives the exact total of all 9 dates instantly!
CBSE Step-by-Step Marking Scheme
Correct total sum (126) 1.5 M
Clear mathematical explanation of multiplying center date by 9 1.5 M
Q6 Birth Certificate Analysis • Bindo's Record
Study Bindo's birth certificate details:
• Date of Birth: 02/05/2012 (2nd May 2012)
• Registration Date: 02/06/2012
(a) In which month and year was Bindo born?
(b) How old was Bindo on 2nd May 2020?
(c) After how many days was the birth registered?
[3 Marks]
✅ Step-by-Step Solution & Working
Birth Certificate Data:
• (a) Birth Month & Year: Born in May 2012 (Month 05 is May).
• (b) Age on 02/05/2020: 2020 - 2012 = 8 years old.
• (c) Registration Duration: From 2nd May to 2nd June = 1 month (or 31 days) later.
CBSE Step-by-Step Marking Scheme
Correct month (May) and year (2012) 1.0 M
Correct age calculation (8 years) 1.0 M
Correct registration duration (1 month / 31 days) 1.0 M
Q7 How Long Does It Take? • Duration Estimates
Categorize the following activities into 'Takes Minutes', 'Takes Hours', and 'Takes Days/Months':
(a) Boiling an egg
(b) Knitting a woolen sweater
(c) Watching a movie
(d) Brushing your teeth
(e) Ripening of a mango on a tree
[3 Marks]
✅ Step-by-Step Solution & Working
Duration Categorization:
• Takes Minutes:
- Brushing your teeth (~2-3 minutes)
- Boiling an egg (~10 minutes)

• Takes Hours:
- Watching a movie (~2-3 hours)

• Takes Days or Months:
- Knitting a sweater (~several days/weeks)
- Ripening of a mango (~a few weeks/months).
CBSE Step-by-Step Marking Scheme
Correct minute-duration activities 1.0 M
Correct hour-duration activities 1.0 M
Correct days/months-duration activities 1.0 M
Q8 Textbook Exercise • Real-Life Math
In Chapter 7 ('Time Goes on...'), a student solves an NCERT word problem: If 1 kg of apples costs ₹60 and 1 kg of oranges costs ₹40, how much do 2 kg of apples and 3 kg of oranges cost altogether?
[3 Marks]
✅ Step-by-Step Solution & Working
Step-by-Step Solution:
1. Cost of 2 kg apples = 2 × ₹60 = ₹120.
2. Cost of 3 kg oranges = 3 × ₹40 = ₹120.
3. Total cost = ₹120 + ₹120 = ₹240.
CBSE Step-by-Step Marking Scheme
Apples = ₹120 1 M
Oranges = ₹120 1 M
Total = ₹240 1 M
Q9 In-Text Activity • Hands-on Investigation
In 'Time Goes on...', how do you measure and compare quantities accurately? Explain with an example using standard units.
[3 Marks]
✅ Step-by-Step Solution & Working
Measurement Explanation:
• Standard units provide consistent and reliable measurements across the world.
• For length, we use metres (m) and centimetres (cm).
• For weight, we use kilograms (kg) and grams (g).
• For liquids, we use litres (L) and millilitres (mL).
• Unlike non-standard units (such as footsteps or handspans), standard units give the exact same measurement no matter who measures.
CBSE Step-by-Step Marking Scheme
Standard units defined 1.5 M
Examples for length, weight, liquid 1.5 M
Q10 Practice Time • Two-Step Word Problem
Suresh bought a school bag for ₹175 and a pencil box for ₹45. He gave a ₹500 note to the shopkeeper. How much change did he receive?
[3 Marks]
✅ Step-by-Step Solution & Working
Step-by-Step Solution:
1. Total money spent = ₹175 + ₹45 = ₹220.
2. Amount paid = ₹500.
3. Change returned = ₹500 - ₹220 = ₹280.
CBSE Step-by-Step Marking Scheme
Total spent = ₹220 1.5 M
Change = ₹280 1.5 M
Q11 Mental Math • Quick Calculations
Calculate mentally without writing long columns:
(a) 250 + 150 = ?
(b) 500 - 180 = ?
(c) 4 × 25 = ?
(d) 100 ÷ 4 = ?
[2 Marks]
✅ Step-by-Step Solution & Working
Mental Calculations:
• (a) 250 + 150 = 400.
• (b) 500 - 180 = 320.
• (c) 4 × 25 = 100.
• (d) 100 ÷ 4 = 25.
CBSE Step-by-Step Marking Scheme
All 4 mental results correct 2 M
Q12 Geometry & Shapes • Edge and Corner Counting
Name a 3D solid shape that has:
(a) 6 flat square faces, 12 straight edges, and 8 corners.
(b) 1 curved surface and 2 flat circular faces.
(c) Only 1 curved surface and 0 corners.
[3 Marks]
✅ Step-by-Step Solution & Working
Solid Shapes:
• (a) 6 square faces, 12 edges, 8 corners: Cube.
• (b) 1 curved and 2 circular faces: Cylinder.
• (c) Only 1 curved surface, 0 corners: Sphere.
CBSE Step-by-Step Marking Scheme
Cube 1 M
Cylinder 1 M
Sphere 1 M
Q13 Pattern Time • Sequences and Rules
Identify the rule and find the next two terms: 5, 10, 20, 40, ___, ___.
[2 Marks]
✅ Step-by-Step Solution & Working
Rule: Each term is multiplied by 2 (doubled).
• 40 × 2 = 80
• 80 × 2 = 160.
Next terms are 80, 160.
CBSE Step-by-Step Marking Scheme
Next terms 80, 160 1 M
Rule: multiplying by 2 1 M
Q14 Time & Calendar • Date Calculation
Rohan's summer vacation starts on 15th May and ends on 30th June. How many total days of vacation does Rohan get? (Remember: May has 31 days).
[3 Marks]
✅ Step-by-Step Solution & Working
Days Count:
• Days in May: From 15th to 31st = (31 - 15) + 1 = 17 days.
• Days in June: Full 30 days = 30 days.
• Total vacation days = 17 + 30 = 47 days.
CBSE Step-by-Step Marking Scheme
May days = 17 1.5 M
June days = 30; Total = 47 days 1.5 M
Q15 Equal Sharing • Division Problem
Mother bakes 36 cookies and wants to distribute them equally among 4 children. How many cookies does each child receive? Write the division sentence.
[2 Marks]
✅ Step-by-Step Solution & Working
Equal Sharing:
• Total cookies = 36.
• Number of children = 4.
• Cookies per child = 36 ÷ 4 = 9 cookies.
• Division sentence: 36 ÷ 4 = 9.
CBSE Step-by-Step Marking Scheme
36 ÷ 4 = 9 cookies 2 M
Q16 Data Handling • Reading a Bar Chart
A survey of pets owned by children: Dog (14), Cat (10), Parrot (6), Fish (8).
(a) Which pet is owned by the least number of children?
(b) How many total pets are there?
(c) How many more dogs are there than parrots?
[3 Marks]
✅ Step-by-Step Solution & Working
Survey Analysis:
• (a) Least owned pet: Parrot (only 6).
• (b) Total pets: 14 + 10 + 6 + 8 = 38 pets.
• (c) Difference: 14 Dogs - 6 Parrots = 8 more dogs.
CBSE Step-by-Step Marking Scheme
Parrot least 1 M
Total = 38 1 M
Difference = 8 1 M
Q17 Money • Making a Change
A toy train costs ₹85. You pay with a ₹100 note. The shopkeeper gives you change in 5-rupee coins only. How many 5-rupee coins do you receive?
[2 Marks]
✅ Step-by-Step Solution & Working
Calculations:
• Change due = ₹100 - ₹85 = ₹15.
• Number of 5-rupee coins = ₹15 ÷ ₹5 = 3 coins.
CBSE Step-by-Step Marking Scheme
Change = ₹15 1 M
3 coins of ₹5 1 M
🌟 NEP 2020 Competency-Based Case Study

Family Mango Tree Planting Record

Grandfather planted a mango sapling in the family orchard in July 2016. The tree bore its first batch of mangoes in July 2021.

Analytical Task: How many years did the sapling take to bear fruit? If it is now July 2026, for how many years has the tree been bearing fruit?
Evaluation & Model Answer:
1. Years to first fruit = 2021 - 2016 = 5 years.
2. Years bearing fruit up to 2026 = 2026 - 2021 = 5 years (or 6 harvest seasons including 2021).
Rubric: 1.5M years to first fruit + 1.5M active fruiting years.
⬅️ Ch 6: Fun with Give and Take Ch 8: Who Is Heavier? ➡️