Chapter 1.1 (Mathematics 9th)

Addition of Integers

Activity 1

  1. Each member of the group to cut two small pieces of paper in rectangular shape.
  2. Each member to write a positive integer on one card and a negative integer on the other.
  3. Each member to place the paper cards in a common container.
  4. Shuffle the cards to mix.
  5. Each member to pick blindly 2 paper cards.
  6. Each member to add the integers on the picked pieces of paper.
  7. Compare the sum obtained by each member of your group and share with other groups.
  8. The one with the highest sum is the winner.

Learning Points

  • Adding two positive integers results in positive integers.
  • Adding two negative integers will result in the sum with a negative sign.
  • The sum of a smaller positive integer and a bigger negative integer is a negative integer.
  • The sum of a bigger positive integer and a smaller negative integer is a positive integer.

Example 1

Work out:

  1. (+5) + (+4)
  2. (–6) + (+2)
  3. (–3) + (–3) + (+5)

Solution

  1. (+5) + (+4) = +9
  2. (–6) + (+2) = –4
  3. (–3) + (–3) + (+5) = –1

Exercise 1

  1. (+7) + (+5) = 
  2. (+11) + (+8) = 
  3. (–13) + (–7) = 
  1. (+15) + (–10) = 
  2. (20) + (–11) = 
  3. (+31) + (–22) = 
  1. (–5) + (–2) + (+3) = 
  2. (–11) + (–14) + (–24) = 
  3. (+16) + (+14) + (–18) = 
  4. (–44) + (–31) + (–8) = 

The average room temperature on a certain day was recorded as 22 ℃. The following day, the average temperature increased by 6 ℃. Find the average room temperature on the second day.

∴  ℃

The temperature of water was recorded as 18 ℃. After heating, its temperature rose by 5 ℃. Find the final temperature of the water.

∴  ℃

The speedometer of a car recorded 30 km/h. The driver increased the speed by 15 km/h. Find the final speed of the car.

∴  km/h

Please wait