- A−10 °C
- B7 °C
- C−7 °C
- D−13 °C
Step-by-Step Solution
Total fall = °C. Starting from 3 °C: °C. Traps: −10 °C reports only the fall and forgets the 3 °C start, while 7 °C works out — subtracting in the wrong order.
Answer: C) −7 °C
The temperature at a hill station is 3 °C and it falls by °C every hour. What will the temperature be after 4 hours?
Class 8Rational NumbersRational Numbers
Key idea: Properties at a glance
| Property | Addition | Subtraction | Multiplication | Division |
|---|---|---|---|---|
| Closure | ✓ | ✓ | ✓ | ✓ (b ≠ 0) |
| Commutative | ✓ | ✗ | ✓ | ✗ |
| Associative | ✓ | ✗ | ✓ | ✗ |
Distributive: multiplication distributes over addition AND subtraction. a × (b + c) = ab + ac, and a × (b − c) = ab − ac.
|---|---|---|---|---|
| Closure | ✓ | ✓ | ✓ | ✓ (b ≠ 0) |
| Commutative | ✓ | ✗ | ✓ | ✗ |
| Associative | ✓ | ✗ | ✓ | ✗ |
Distributive: multiplication distributes over addition AND subtraction. a × (b + c) = ab + ac, and a × (b − c) = ab − ac.
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