1718 WB1Y CH6+9 Lesson 7

• Wiskunde
• Middelbare school
• vwo
• Leerjaar 1

Which exercises should I discuss on the board?

Recap: Writing formulas shorter

- Replace the variables with one letter for each variable
- Remove the multiplication sign (x), always write the number before the letter.
15 - 3 x time = height  can be written shorter as 15 - 3t = h

Write the formula as short as possible
price = 3 + 1.5 x number of chocolates

Write the formula as short as possible
24 - time x 4 = height

More writing formulas shorter

In formulas that contain brackets can be written shorter too, by removing the multiplication sign.
p = 10 + 2 x (t - 5) can be written shorter as
p = 10 + 2(t - 5)

a = 2.5 x (d + 2) + 4 can be written shorter as
a = 2.5(d+2) + 4

Write the formula as short as possible
r = 3 + 2 x (q - 4)

Working with (shortened) formulas

When using a shortened formula, remember that there is an "invisible" multiplication sign!

h = 19 - 2t corresponds to a candle. Here h is the height of a candle in cm and t is the time in hours. Calculate the height of the candle after 6 hours.

Working with (shortened) formulas

When using a shortened formula, remember that there is an "invisible" multiplication sign!
h = 19 - 2t corresponds to a candle. Here h is the height of a candle in cm and t is the time in hours. Calculate the height of the candle after 6 hours.

•  6 hours corresponds to t = 6. Replace t with the number 6 in the formula and add the "invisible" multiplication sign. Calculate following the order of operations.
  
• h = 19 - 2 x 6 = 19 - 12 = 7
• The height of the candle after 6 hours is 7 cm.
  

Working with (shortened) formulas

The formula q = 12 - 5(t + 2) is given.
Calculate q when t = 4.

• Replace t with 4 and add the "invisible" multiplication sign. Calculate following the order of operations.
  
• q = 12 - 5x(4 + 2)= 12 - 5 x 6 = 12 - 30 = -18
• When t = 4, q = -18
  

Calculate a when c = 3
a = 5c - 2

1. 51
2. 6
3. 13
4. 9

Calculate y when t = -2
y = 10 + 3t

1. 16
2. 4
3. 11
4. -26

Calculate h when t = 6
h = 5 + 3(t - 1)

1. 20
2. 40
3. 13
4. something else

Calculate p when n = -3
p = 20 - 5(n+1)

1. 40
2. 10
3. 0
4. something else

Homework Tuesday

§9.2, make and correct:
7, 8, 9, 10, 11, 12, 13, 15
(so not 14)