Question 9 of 58intermediate💡 UnderstandShort Answer2 marks

Explain, using a real-world example of debt, why subtracting a negative number is the same as adding a positive number (e.g., 10−(−5)=1510 - (-5) = 15).

Correct Answer

In the real world, a negative number represents a debt. For instance, −5-5 represents a debt of ₹5 that you owe.

Subtracting a negative number represents the removal of that debt. If you currently have ₹10 and someone takes away your debt of ₹5, you no longer owe that amount.

By taking away the debt, your overall wealth effectively increases by ₹5. You are now ₹5 richer, making your total ₹15. This shows why subtracting a negative number is the same as adding a positive number: 10−(−5)=1510 - (-5) = 15.

Exercise: Exercise Set 3.2 | Q: 4 | (Page 6)
For More Understanding

Explanation

The textbook uses the concept of 'debt' (Riña) for negative numbers and 'fortune' (Dhana) for positive numbers. The 'Think and Reflect' section explains that taking away a debt makes you richer, which directly applies to the subtraction of negative numbers. Removing a debt of 5 (-5) from a fortune of 10 increases your net worth by 5, hence 10 - (-5) = 15.

Solution Steps

  1. Step 1: Identify that a negative number represents a debt (e.g., -5 is a debt of ₹5).

  2. Step 2: Understand that subtracting a negative number means removing that debt.

  3. Step 3: Realize that removing a debt increases your wealth, which is the same as adding a fortune.

  4. Step 4: Conclude that 10 - (-5) = 10 + 5 = 15.

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