Explain, using a real-world example of debt, why subtracting a negative number is the same as adding Class 9

Explain, using a real-world example of debt, why subtracting a negative number is the same as adding Class 9

Question 1.

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) = 15). Class 9

Solution:

Real-world example:

Imagine you are in Shimla on a winter morning. The temperature is 10°C. The effect of a decrease of 5°C is removed by sunlight, so the temperature rises by 5°C. Mathematically: 10 - (-5) = 10 + 5 = 15°C

Similarly, in mathematics, subtracting a negative number is the same as adding a positive number.

Question 2.

Can you explain why we need q t 0 in the definition of a rational number? Class 9

Answer:

If q = 0, then $\frac{p}{q}=\frac{p}{0^{\prime}}$, which represents division by zero.

But division by zero is not defined.

From Brahmagupta's rule: a × 0 = 0, for every number a.

If $\frac{p}{0}$ were defined, then multiplying that value by 0 should give p.

But any number multiplied by 0 always gives 0, not p.

This creates a contradiction.

Therefore, in the definition of a rational number, we must have q ≠ 0.