Chapter 3.6 (Mathematics 5)

Patterns involving subtraction

Patterns involving subtraction

Group Activity 6

In groups of five:

  1. Draw a line 5 metres (500 cm) long on the floor.
  2. Mark and label on the line equal intervals of length 50 cm as shown.
  1. Starting from 500 cm move backwards at intervals of 50 cm and stop at each point marked. Record the number at each point.
  2. List the numbers in order starting with 500. What do you notice?
  3. Discuss the activity and share with other groups.

Example 6

Mueni had Sh 60 000 in a bank. She withdrew Sh 5 000 every time she visited the bank. Write the amount of money remaining in the bank after every withdrawal for 6 visits.

  • 1st visit 60 000 – 5 000 = 55 000
  • 2nd visit 55 000 – 5 000 = 50 000
  • 3rd visit 50 000 – 5 000 = 45 000
  • 4th visit 45 000 – 5 000 = 40 000
  • 5th visit 40 000 – 5 000 = 35 000
  • 6th visit 35 000 – 5 000 = 30 000

Amount of money left in Ksh in the bank: 55 000, 50 000, 45 000, 40 000, 35 000, 30 000.

Note

To create a number pattern involving subtraction, subtract the same number.

Exercise F

In pairs:

F1

Use the rule to create a pattern of five numbers in each of the following:

  1. 775 000; “Subtract 1 000”
  2. 86 000; “Subtract 2 000”

F2

In each of the following patterns, state the rule used:

  1. 80 000, 60 000, 40 000, 20 000
  2. 30 000, 25 000, 20 000, 15 000
  3. 900 000, 850 000, 800 000, 750 000
  1. 420 000, 400 000, 380 000,
    , , 
  2. 650 000, 640 000, 630 000,
    , , 
  3. 999 000, 909 000, 819 000,
    , , 

F5

Mdoe has 900 kg of groundnuts. He sells 50 kg per day for 7 days. Write in order the amount of groundnuts remaining each day for 7 days.

F6

There were 240 people to be transported to a security meeting. The people were transported using a minibus that could only carry 30 people per trip. Write down in order the number of people remaining to be transported each time.

F7

In groups, make three patterns each of 5 numbers involving subtraction.