Money — Class 5 Mathematics (Samacheer Kalvi)
TN State Board (Samacheer Kalvi) Class 5 Mathematics, Term 3 Unit. Addition and subtraction on money, and multiplication and division in money.
1. Writing money
1 rupee = 100 paise
An amount is written with a dot between the two parts: ₹45.75 means 45 rupees and 75 paise.
The two digits after the dot are always paise, and there must be exactly two of them. So ₹8.50 is eight rupees and fifty paise, while five paise would be written ₹8.05.
Converting. Rupees into paise, multiply by 100. Paise into rupees, divide by 100.
- ₹6 = 600 paise
- ₹4.25 = 425 paise
- 350 paise = ₹3.50
2. Adding money
Line up the dots one under the other, keep the paise column two digits wide, and carry a rupee whenever the paise reach 100.
Add ₹45.75 and ₹23.50:
| ₹ | paise | |
|---|---|---|
| 45 | 75 | |
| + | 23 | 50 |
| 69 | 25 |
The paise gave 75 + 50 = 125, which is ₹1 and 25 paise, so 25 stays and the rupee is carried: 45 + 23 + 1 = 69. The answer is ₹69.25.
3. Subtracting money
Same columns, and borrow ₹1 as 100 paise when the top paise are too small.
Subtract ₹18.60 from ₹50.25. Since 25 is less than 60, borrow a rupee: 125 − 60 = 65 paise, and 49 − 18 = 31. The answer is ₹31.65.
4. Multiplying money
To find the cost of several identical items, multiply.
Total cost = cost of one item × number of items
One notebook costs ₹28.50. What do 4 notebooks cost?
Multiply the paise and the rupees separately: 50 × 4 = 200 paise = ₹2, and 28 × 4 = ₹112. Adding the carried ₹2 gives ₹114.
A quicker route for awkward amounts is to convert to paise first, multiply, then convert back: ₹28.50 is 2850 paise, and 2850 × 4 = 11,400 paise = ₹114.
5. Dividing money
Division answers two different questions, and it is worth seeing which one is being asked.
Sharing equally. Four friends share ₹250 equally. Each gets 250 ÷ 4 = ₹62.50.
Finding the cost of one. If 5 pens cost ₹75, then one pen costs 75 ÷ 5 = ₹15. That is the rate.
Cost of one item = total cost ÷ number of items
When the division does not come out evenly in rupees, convert to paise. For ₹250 ÷ 4, that is 25,000 paise ÷ 4 = 6250 paise = ₹62.50.
6. Bills and change
A bill lists what was bought, how much of it, and what it cost. For each line, multiply the quantity by the rate. Then add the amounts for the total.
| Item | Quantity | Rate | Amount |
|---|---|---|---|
| Notebook | 4 | ₹28.50 | ₹114.00 |
| Pen | 3 | ₹15.00 | ₹45.00 |
| Eraser | 2 | ₹5.50 | ₹11.00 |
| Total | ₹170.00 |
Change = amount paid − total
Paying that bill with a ₹200 note gives change of 200 − 170 = ₹30.
7. Worked examples
Example 1. Convert ₹7.40 into paise.
Solution: (7 × 100) + 40 = 740 paise.
Example 2. Convert 925 paise into rupees.
Solution: 925 ÷ 100 = ₹9.25.
Example 3. Add ₹32.60 and ₹18.75.
Solution: Paise: 60 + 75 = 135, which is ₹1 and 35 paise. Rupees: 32 + 18 + 1 = 51. Answer ₹51.35.
Example 4. Subtract ₹27.85 from ₹60.40.
Solution: 40 is less than 85, so borrow: 140 − 85 = 55 paise, and 59 − 27 = 32. Answer ₹32.55.
Example 5. One kilogram of sugar costs ₹42.50. Find the cost of 6 kg.
Solution: ₹42.50 is 4250 paise. 4250 × 6 = 25,500 paise = ₹255.
Example 6. Six friends share ₹45 equally. Find each share.
Solution: 45 ÷ 6 = 7.50, so each gets ₹7.50.
Example 7. If 8 pencils cost ₹60, find the cost of one pencil.
Solution: 60 ÷ 8 = ₹7.50.
Example 8. A bill comes to ₹368.50 and is paid with a ₹500 note. Find the change.
Solution: 500 − 368.50 = ₹131.50.
8. Practice
- How many paise make one rupee?
- Convert ₹12.05 into paise.
- Convert 1480 paise into rupees.
- Add ₹56.45 and ₹28.80.
- Subtract ₹19.90 from ₹75.35.
- One book costs ₹64.50. Find the cost of 3 books.
- Seven friends share ₹210 equally. Find each share.
- If 5 notebooks cost ₹142.50, find the cost of one notebook.
- Find the total for 2 kg of rice at ₹58.50 per kg and 3 pens at ₹12 each.
- That total is paid with a ₹200 note. Find the change.
9. Answers
- 100 paise.
- 1205 paise.
- ₹14.80.
- Paise 45 + 80 = 125, so carry ₹1: 56 + 28 + 1 = 85. Answer ₹85.25.
- 35 is less than 90, so borrow: 135 − 90 = 45 paise, and 74 − 19 = 55. Answer ₹55.45.
- ₹64.50 is 6450 paise; 6450 × 3 = 19,350 paise = ₹193.50.
- 210 ÷ 7 = ₹30.
- 142.50 ÷ 5 = ₹28.50.
- Rice 2 × 58.50 = ₹117 and pens 3 × 12 = ₹36, so the total is ₹153.
- 200 − 153 = ₹47.
10. Summary
- 1 rupee = 100 paise, and exactly two digits follow the dot.
- Rupees into paise multiply by 100; paise into rupees divide by 100.
- Line up the dots when adding or subtracting, carrying or borrowing ₹1 as 100 paise.
- Total cost = cost of one item × number of items.
- Cost of one item = total cost ÷ number of items, which is the rate.
- Converting to paise first makes awkward multiplications and divisions straightforward.
- On a bill, amount = quantity × rate, and the total is the sum of the amounts.
- Change = amount paid − total.
