In deze les zitten 13 slides, met interactieve quiz en tekstslides.
Lesduur is: 50 min
Onderdelen in deze les
Which exercises should we discuss on the board?
Slide 1 - Woordweb
Calculating with percentages in a ratio table
When working with percentages, a ratio table is an easy way to show your calculations.
This works for questions where you are given the amounts and have to calculate the percentage, but also for questions where you are given the percentages and have to calculate the amount.
Only round off your final answer!
Slide 2 - Tekstslide
Calculating with percentages in a ratio table
Example: amount --> percentage
In class 2R, 21 pupils cycle to school, 7 take the bus and 2 walk to school. What percentage of pupils takes the bus?
Slide 3 - Tekstslide
Calculating with percentages in a ratio table
Example: amount --> percentage
In class 2R, 21 pupils cycle to school, 7 take the bus and 2 walk to school. What percentage of pupils takes the bus?
Make a ratio table with the total number of pupils (100%), an empty column and the number of pupils asked (7)
Slide 4 - Tekstslide
Calculating with percentages in a ratio table
Example: amount --> percentage
In class 2R, 21 pupils cycle to school, 7 take the bus and 2 walk to school. What percentage of pupils takes the bus?
Make a ratio table with the total number of pupils (100%), an empty column and the number of pupils asked (7)
The known numbers are in the top row, so calculate the percentage for 1 pupil and use this to calculate the percentage for 7 pupils.
Slide 5 - Tekstslide
Calculating with percentages in a ratio table
Example: amount --> percentage
In class 2R, 21 pupils cycle to school, 7 take the bus and 2 walk to school. What percentage of pupils takes the bus?
Make a ratio table with the total number of pupils (100%), an empty column and the number of pupils asked (7)
The known numbers are in the top row, so calculate the percentage for 1 pupil and use this to calculate the percentage for 7 pupils.
Slide 6 - Tekstslide
Calculating with percentages in a ratio table
Example: amount --> percentage
In class 2R, 21 pupils cycle to school, 7 take the bus and 2 walk to school. What percentage of pupils takes the bus?
Answer: 23% take the bus.
Important: Do NOT round of the
percentage for 1 pupil on your
calculator. Short calculation:
Slide 7 - Tekstslide
Calculating with percentages in a ratio table
Example: percentage --> amount
In class 2R, there are 30 pupils. 47% of the pupils scored above a 9 on the test of chapter 2. How many pupils were this?
Slide 8 - Tekstslide
Calculating with percentages in a ratio table
Example: percentage --> amount
In class 2R, there are 30 pupils. 47% of the pupils scored above a 9 on the test of chapter 2. How many pupils were this?
Make a ratio table with the total number of pupils (100%), an empty column and a column with the percentage asked (47%)
Slide 9 - Tekstslide
Calculating with percentages in a ratio table
Example: percentage --> amount
In class 2R, there are 30 pupils. 47% of the pupils scored above a 9 on the test of chapter 2. How many pupils were this?
Make a ratio table with the total number of pupils (100%), an empty column and a column with the percentage asked (47%)
The known numbers are in the bottom row, so calculate how many pupils go with 1% and use this to calculate how many pupils go with 47%
Slide 10 - Tekstslide
Calculating with percentages in a ratio table
Example: percentage --> amount
In class 2R, there are 30 pupils. 47% of the pupils scored above a 9 on the test of chapter 2. How many pupils were this?
Make a ratio table with the total number of pupils (100%), an empty column and a column with the percentage asked (47%)
The known numbers are in the bottom row, so calculate how many pupils go with 1% and use this to calculate how many pupils go with 47%
Slide 11 - Tekstslide
Calculating with percentages in a ratio table
Example: percentage --> amount
In class 2R, there are 30 pupils. 47% of the pupils scored above a 9 on the test of chapter 2. How many pupils were this?
Answer: 14 pupils scored above a 9.
IMPORTANT: Round off sensibly.
You cannot have 0.1 pupils.
Slide 12 - Tekstslide
Homework Monday 10-9
Bring a pair of compasses (and your usual stuff)
Make the exercises from your chosen path from §2.1