The Fish Tale — Class 5 Mathematics (CBSE)

Based on the NCERT Math Magic Grade 5 textbook. Read the story, understand the numbers, then solve the practice set without looking at the answers.

1. Why this chapter matters

The Fish Tale uses a fisherman's daily life to teach large numbers and practical maths. Students learn to read and write numbers up to crores, compare large quantities, calculate speed-distance-time, and solve profit-loss problems. This chapter connects classroom maths to real-world earning and spending, making abstract numbers feel meaningful.

Fishing is a major livelihood in coastal India. Through this context, students also develop awareness of different occupations and how mathematics is used in everyday trade.

2. Place value up to crores

In Class 5, students extend their understanding of the place value system beyond lakhs to crores.

Key rule: In the Indian number system, commas are placed after every two digits starting from the right after the first three digits. For example, 5,73,25,891 is read as five crore seventy-three lakh twenty-five thousand eight hundred ninety-one.

3. Reading and writing large numbers

Practice converting between words and figures.

• 1,25,00,000 — One crore twenty-five lakh
• 3,40,75,600 — Three crore forty lakh seventy-five thousand six hundred
• Twelve lakh fifty thousand — 12,50,000
• Eighty-four lakh seven hundred — 84,07,00

Important terms

4. Speed, distance, and time

Fishermen travel long distances into the sea. The relationship between speed, distance, and time is:

• Distance = Speed x Time
• Speed = Distance / Time
• Time = Distance / Speed

Example 1: A boat travels at 15 km per hour for 4 hours. How far does it go?

Distance = 15 x 4 = 60 km

Example 2: A fish swims 120 metres in 4 minutes. What is its speed?

Speed = 120 / 4 = 30 metres per minute

Example 3: A fishing boat needs to cover 90 km. Its speed is 18 km per hour. How much time will it take?

Time = 90 / 18 = 5 hours

5. Profit and loss

Fishermen buy fish from the shore, sell it in the market, and earn money. Understanding profit and loss is essential.

• Profit = Selling Price — Cost Price (when SP > CP)
• Loss = Cost Price — Selling Price (when CP > SP)

Example 1: A fisherman buys 20 kg of fish at Rs 80 per kg. He sells it at Rs 110 per kg. What is his profit?

Cost Price = 20 x 80 = Rs 1,600 Selling Price = 20 x 110 = Rs 2,200 Profit = 2,200 — 1,600 = Rs 600

Example 2: A vendor buys 50 kg of prawns at Rs 200 per kg. Due to bad weather, he sells at Rs 180 per kg. What is his loss?

Cost Price = 50 x 200 = Rs 10,000 Selling Price = 50 x 180 = Rs 9,000 Loss = 10,000 — 9,000 = Rs 1,000

6. Comparing large numbers

When comparing large numbers, first check the number of digits. The number with more digits is larger.

7. Activity corner

Activity 1: Visit a local fish market or vegetable market. Note the prices of three items. Calculate the total cost of buying 5 kg of each. Find the profit if sold at a higher rate.

Activity 2: Find the distance between your home and school. If you walk at 4 km per hour, how long does it take? If you cycle at 12 km per hour, how long does it take?

Activity 3: Write five large numbers from newspapers or grocery bills. Read them aloud and write them in words.

8. Common mistakes

• Mistake: Placing commas incorrectly in the Indian number system Fix: Remember the pattern — ones, tens, hundreds (3 digits), then lakhs and crores in pairs.
• Mistake: Confusing 'profit on each item' with 'total profit' Fix: Always multiply or add correctly: total profit = profit per item x number of items.
• Mistake: Forgetting to convert units in speed-distance-time problems Fix: Keep all units the same. If speed is in km/h, time must be in hours.

9. Key facts

• 1 lakh = 1,00,000 (one hundred thousand)
• 1 crore = 1,00,00,000 (one hundred lakhs)
• Distance = Speed x Time
• Profit = Selling Price — Cost Price
• Loss = Cost Price — Selling Price
• Always write the unit (km, m, Rs, kg) with every answer.
• Use estimation to check if your answer is reasonable.

10. Self-test

1. Write 3,40,75,600 in words.
2. Which is larger: 45,00,000 or 54,00,000?
3. A boat travels at 12 km per hour for 3 hours. What distance does it cover?
4. A fisherman buys 30 kg of fish at Rs 90 per kg. He sells all at Rs 120 per kg. Find his profit.
5. A vendor sells 25 kg of prawns. She buys at Rs 250 per kg and sells at Rs 220 per kg. What is her loss?

11. Answer key

1. Write 3,40,75,600 in words. Answer: Three crore forty lakh seventy-five thousand six hundred.

2. Which is larger: 45,00,000 or 54,00,000? Answer: 54,00,000 (fifty-four lakh). When both have the same digits, compare the leftmost different digit. 54 is greater than 45.

3. A boat travels at 12 km per hour for 3 hours. What distance does it cover? Answer: Distance = 12 x 3 = 36 km.

4. A fisherman buys 30 kg of fish at Rs 90 per kg. He sells all at Rs 120 per kg. Find his profit. Answer: CP = 30 x 90 = Rs 2,700. SP = 30 x 120 = Rs 3,600. Profit = 3,600 — 2,700 = Rs 900.

5. A vendor sells 25 kg of prawns. She buys at Rs 250 per kg and sells at Rs 220 per kg. What is her loss? Answer: CP = 25 x 250 = Rs 6,250. SP = 25 x 220 = Rs 5,500. Loss = 6,250 — 5,500 = Rs 750.

12. Quick revision

• Review place value up to crores in the Indian number system.
• Practise reading and writing large numbers in both figures and words.
• Remember the three formulas: Distance = Speed x Time, Profit = SP — CP, Loss = CP — SP.
• Use a table to organise data in word problems.
• Check your answer — does it make sense in the story context?
• Learn by doing the activity once, not by memorising only the final answers.