✅ SOLUTIONS
Class 5
Chapter 12: Racing Seconds
Math Mela · NCERT Solutions
Class 5Math Mela (NCERT)Chapter 12
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🧘 Yoga Clocks — Let Us Find Out
Start/finish time of yoga; duration; elapsed time problems; painting table.
Solution
| Q | Answer |
|---|---|
| 1. Start time | 5:35 (reading clock 1 — hour hand just before 6, minute hand at 7) |
| 2. Finish time | 5:55 (reading clock 2 — hour hand just before 6, minute hand at 11) |
| 3. Duration | 5:55 − 5:35 = 20 minutes |
Q4. Elapsed time:
| Period | Answer |
|---|---|
| (a) 01:15pm to 01:42pm | 27 minutes |
| (b) 03:18pm to 08:18pm | 5 hours (same minutes, just count hours) |
| (c) 09:15am to 11:30am | 2 hours 15 minutes |
Q5. Painting time — Raghav 1h20m, Rani 2h10m, Ritu 1h35m:
(a) Longest: Rani (2 hours 10 min)
(b) Least: Raghav (1 hour 20 min)
🕐 12-Hour/24-Hour Format Tables
Q6. Fill in the blanks.
Solution
| 12-hour | 24-hour |
|---|---|
| 05:30 a.m. | 05:30 hours (given) |
| 08:35 a.m. | 08:35 hours |
| 11:55 a.m. | 11:55 hours |
| 02:30 p.m. | 14:30 hours (given) |
| 05:30 p.m. | 17:30 hours |
| 09:35 p.m. | 21:35 hours |
Q7. Match 12-hour to 24-hour format.
Solution
| 12-hour | 24-hour |
|---|---|
| 06:30 a.m. | 06:30 hours |
| 08:45 p.m. | 20:45 hours |
| 11:45 p.m. | 23:45 hours |
| 04:30 a.m. | 04:30 hours |
| 07:30 p.m. | 19:30 hours |
| 01:30 a.m. | 01:30 hours |
🏃 School Race & Seconds/Minutes Activities
Akira, Sunita, Mary — 200m race, times 01:55, 01:56, 01:57. Who won?
Solution
Each took just over 1 minute: 01:55 = 1 min 55 sec, 01:56 = 1 min 56 sec, 01:57 = 1 min 57 sec.
The winner is whoever has the SMALLEST time — 1 minute 55 seconds (115 seconds total) — since finishing FASTEST means taking the LEAST time!
Seconds or Minutes? Tick the appropriate unit for each activity.
Solution
| Activity | Unit |
|---|---|
| Blinking of eyes | Seconds |
| Switching lights on/off | Seconds |
| Counting from 1-20 | Seconds |
| Filling a glass from the tap | Seconds |
| Melting of an ice-cube | Minutes |
| Making a phone call | Minutes |
| Sitting down on the floor | Seconds |
| Drinking a glass of water | Seconds |
| Snapping fingers | Seconds |
| Washing hands | Seconds (about 20-30 sec) |
🕑 Reading Clocks (Seconds Hand)
Read the before/after clocks and find elapsed seconds.
Solution
📎 Four before/after clock pairs showing the seconds hand movement
| # | Activity | Seconds hand: Before → After | Elapsed time |
|---|---|---|---|
| 1 | Rani, out of bed | 12 (0s) → 6 (30s) | 30 seconds |
| 2 | Raghav, room to kitchen | 12 (0s) → 7 (35s) | 35 seconds |
| 3 | Ritu, pick up paper | 9 (45s) → 12 (60s) | 15 seconds |
| 4 | Raghu, wash spoon & plate | Full revolution back to start | 60 seconds |
💡 Reading a seconds hand: each number on the clock face = 5 seconds (since 12 numbers × 5 = 60 seconds in a full circle). Count how many 5-second "jumps" the hand made!
✏️ Drawing Missing Seconds Hands
Draw the seconds hand for each given duration.
Solution
| # | Duration | Draw hand pointing to |
|---|---|---|
| 1 | 20 seconds | the "4" position (20÷5=4) |
| 2 | 30 seconds | the "6" position (30÷5=6) |
| 3 | 60 seconds | the "12" position (full circle back to start) |
| 4 | 40 seconds | the "8" position (40÷5=8) |
🔄 Hours ↔ Minutes ↔ Seconds Conversions
1(a). Double number line: hours ↔ minutes.
Solution
hr: 1, 2, 4, 7, 8, 9, 11, 12 | min: 60, 120, 240, 420, 480, 540, 660, 720
1(b). Time conversions (i-viii).
Solution
| Problem | Answer |
|---|---|
| (i) 1hr 10min | 70 min |
| (ii) 2hr 45min | 165 min |
| (iii) 3hr 15min | 195 min |
| (iv) 4hr 20min | 260 min |
| (v) 75 min | 1 hr 15 min |
| (vi) 150 min | 2 hr 30 min |
| (vii) 220 min | 3 hr 40 min |
| (viii) 390 min | 6 hr 30 min |
1(c). Seconds conversions (i-vii).
Solution
| Problem | Answer |
|---|---|
| (i) 320 sec | 5 min 20 sec |
| (ii) 225 sec | 3 min 45 sec |
| (iii) 700 sec | 11 min 40 sec |
| (iv) 1,000 sec | 16 min 40 sec |
| (v) 10 min 13 sec | 613 sec |
| (vi) 4 min 8 sec | 248 sec |
| (vii) 15 min 40 sec | 940 sec |
Q2. Raghav studies 4 subjects, 50 min each. Total time?
Solution
4 × 50 = 200 min = 3 hours 20 minutes
Q3. Raghu: 08:00 to 09:05 hours.
Solution
1 hour 5 minutes(given/worked example)
✏️ Time Word Problems (Q4-10)
Find the resulting/starting time in each scenario.
Solution
| # | Problem | Working | Answer |
|---|---|---|---|
| 4 | Jyoti: out 6:15PM, +1h45m | 6:15+1:45 | 8:00 PM |
| 5 | Ragini: finished 9:40PM, took 1h10m — start time? | 9:40−1:10 | 8:30 PM |
| 6 | Picnic: left 8:30AM, +4h10m | 8:30+4:10 | 12:40 PM |
| 7 | Raji: started 6:00PM, +1h30m | 6:00+1:30 | 7:30 PM |
| 8 | Alya: out 5:30PM, +1h10m | 5:30+1:10 | 6:40 PM |
| 9 | Lunch: starts 12:30PM, +35min | 12:30+0:35 | 1:05 PM |
| 10 | Now 8:35PM, +8h25m | 8:35PM+8:25 | 5:00 AM (next day) |
💡 For problem 10: 8:35 PM + 8 hours = 4:35 AM (crossing midnight), then +25 more minutes = 5:00 AM.