7H Multiplying decimals

• Wiskunde
• Middelbare school
• vwo
• Leerjaar 2

Good morning!

Schedule: 

• Learning goals 
• Last time
• Multiplying decimals
• Work

Learning goals 

At the end of this lesson I can:

• Calculate multiplications with decimal numbers 
• Calculate decimal multiplications from context problems

What did we do last time?

Amar saved €81.75 for christmas gifts, Maria saved €45.47 for christmas gifts.
How much did they save together?

Calculate 23 ⋅ 425
(without a calculator!)

1. 9775
2. 2125
3. 448
4. 16015

Multiplying decimals 

€1 (Euro) exchanges for ¥7.47 (Chinese Yen)

How much Chinese Yen is equal to €100? 

How much Chinese Yen is equal to €15? 

Multiplying decimals

 €15 =  ¥_________

 15 ⋅ 7.47 =

15  ⋅ 747 = 

Calculate 3.41 ⋅ 1.2

Multiplying decimal

Lucy has a beautiful garden of 24.5 m by 6.74 m. 

What is the area of her garden? 

What is the area of the garden?

Multiplying decimals

Step by step plan:

1. Multiply both numbers by a power of 10 to make whole numbers. 

2. Calculate the new multiplication

3. Count how many powers of 10 you multiplied the numbers with in step 1. 

4. Divide your final answer by as many powers of 10 as you found in step 3

5. Check if you answer makes sense by estimating 

     3.2 ⋅ 4.2 = 

1.   32 ⋅ 42 =

2.  32 ⋅ 42 = 1344

3. 3.2 ⋅ 10 = 32

    4.2 ⋅ 10 = 42

4. 1344 ÷ 100 = 13.44

5. estimation: 3  ⋅  4 = 12

12 is close to 13.44 so my answer makes sense

Let's get to work! 

p. 147 : 7J              1abcd, 2cgk, 3, 4adg, 5cf, 6ab,                                        8, 10

                                  

Finished? 

MyiMaths: