Why does a negative times a negative equal a positive? Think of it in terms of action and debt. Class 9

Why does a negative times a negative equal a positive? Think of it in terms of action and debt. Class 9

Question 1.

Why does a negative times a negative equal a positive? Think of it in terms of action and debt. Class 9

Answer:

A negative number represents a debt, and multiplying by a negative number represents the removal of that debt.

For example, (-3) × (-4) means removing 4 debts of ₹3 each.

If one debt of ₹3 is removed, the person becomes ₹ 3 richer. Similarly, removing 4 such debts makes the person ₹ 12 richer. Therefore, (-3) × (- 4) = +12

Question 2.

The temperature in the high-altitude desert of Ladakh is recorded as 4° C at noon. By midnight, it drops by 15° C. What is the midnight temperature? Class 9

Solution:

Initial temperature = 4°C.

By midnight, the temperature drops by 15°C.

∴ Midnight temperature = 4 - 15 = -11°C

∴ The midnight temperature is -11°C.