Summary
Directed numbers are numbers with both size and direction, where one direction is positive and the other is negative. They are used in arithmetic operations and help in understanding real-life situations involving gains and losses.
- Directed Numbers — numbers with both size and direction, positive or negative. Example: Temperature can be above zero (positive) or below zero (negative).
- Positive Numbers — represent gains or values above zero. Example: A deposit of $100 is a positive number.
- Negative Numbers — represent losses or values below zero. Example: A withdrawal of $50 is a negative number.
Exam Tips
Key Definitions to Remember
- Directed numbers are numbers with both size and direction.
- Positive numbers represent gains or values above zero.
- Negative numbers represent losses or values below zero.
Common Confusions
- Confusing the direction of positive and negative numbers.
- Misapplying the rules for adding and subtracting directed numbers.
Typical Exam Questions
- What temperature is it at midnight if it drops 8 degrees from 4°C? -4°C
- What is the temperature at 7 p.m. if it drops 11°C from 8°C at noon? -3°C
- If it is 4 p.m. at Greenwich, what time is it in Abu Dhabi? 8 p.m.
What Examiners Usually Test
- Understanding and applying the rules of arithmetic operations with directed numbers.
- Comparing and ordering directed numbers.
- Solving real-life problems involving temperature changes and time differences.