1718 WB1Y CH10 Lesson 6

• Wiskunde
• Middelbare school
• vwo
• Leerjaar 1

Which exercises/theory should I discuss on the board?

What is 5.384921 rounded to three decimal places?

1. 5.38
2. 5.384
3. 5.385
4. 5.395

5.384921
The 4th decimal is a 9, this means the 3rd decimal should increase by 1.
5.385

What is 0.19523 rounded to two decimal places?

1. 0.19
2. 0.20
3. 0.2
4. 0.30

0.19523
The 3rd decimal is a 5, this means the 2nd decimal should increase by 1. Since this makes 10, the 1st decimal is increased by 1. A 0 is written in the 2nd decimal place, because you have to have two decimal places.
0.20

Solve the equation. Give your answer as an approximation accurate to 2 decimal places.
10 - 3a = 15

1. 1​3​​2​​
2. −1​3​​2​​
3. 1.67
4. -1.67

Notation                                                     What you might think
10 - 3a = 15                                                 10 + 5  = 15, so 10 - -5 = 15
3a = -5                                                          then 3a = -5
                                                                        3 x a = -5, then a = -5 : 3
                                                                        -5 : 3 in my calculator gives
                                                                         1.666666667, so rounded off
                                                                         to two decimal places is 1.67

a=−​3​​5​​≈1.67

Solve the equation.
Give an exact answer
3.5a + 8 = 9

1. 0.285714286
2. 1
3. ​3.5​​1​​
4. ​7​​2​​

Notation                                     What you might think
3.5a + 8 = 9                               9 - 8 = 1, so 1 + 8 = 9
3.5a = 1                                      then 3.5a = 1
                                                      3.5 x a = 1, then a = 1 : 3.5
                                                      you cannot have a fraction with a       
                                                      decimal number, so multiply the         
                                                     numerator and denominator with 2.

a=​3.5​​1​​=​7​​2​​

What is the first step when making a formula from a graph?

1. shorten the formula
2. calculate the gradient
3. find the start value
4. make a table

Graph -> Formula

1) Make a table (horizontal axis top row, vertical axis bottom row) and fill in some easy to read off points on the graph (grid points).
2) Calculate the gradient (steps in the bottom row divided by the steps in the top row)
3) Find the start value (value in the bottom row when the value in the top row is 0)
4) Make a formula:
start value +/- gradient x top row variable = bottom row variable

Homework Monday

Make and correct all exercises from the studyplanner up to and including §10.6:
36, 37, 38, 39, 40, 41, 42