2. Unit Price： ￡1.05 ①1.05+1.05+1.05= ② 3×1.05= What is the total price?
Now i want to buy three,
What is the total price?
① =
② 3×1.05=

3. Multiply a Decimal
by a Whole Number

4. Group Discussion:1.05×3=?

5. Group Discussion:1.05×3=? 3 pounds 15 pence Solution 1：
3 pounds and 15 pence equals ￡ 3.15.

6. Group Discussion:1.05×3=? 105 pence×3=315 pence
Solution 2：
￡ 1.05 equals 105 pence
105 pence×3=315 pence
315 pence equals ￡ 3.15

7. Review step by step: 1.05×3 =105×3 =315÷100 ÷100 =3.15
How to do the decimal multiplied by a whole number?

8. Conclusion : 1. Transform the decimal into a whole number.
2. Decrease the result based on how many times we have expanded the decimal.

9. Example 1
Get the product of 1.05× 3by vertical
×100
1.05
105 × ×
÷100
3.15
315

10. Summary
(1) Multiply the factor 1.05 by 100 to make it 105, so that the decimal factor is transformed into a whole number factor.
(2) The product will be enlarged because the transformation from 1.05 to 105, so to keep the product unchanged, we have to divide the product by 100.

11. What’s the familiarity between these two methods?
Compare
What’s the familiarity between these two methods?
1.05×3
=105×3÷100
=315÷100
=3.15
1.05 ×
3.15
Two methods are both transform decimal factor to whole number factor.

12. Try your best ！
Which one of the following facts has the biggest product?
(1) × 99.99
(2) × 999.9
(3) × 999.9
(4) × 99.99

13. 1.02×3= Unit Price： ￡ 1.02 What is the total price
On sale!
Unit Price：
￡ 1.02
What is the total price
if i still want to buy three of them?
1.02×3=

14. Fluency Makes Skilled

15. First estimate and then calculate
（1）6×0.9
（2）1.8×2
（3）7×3.5

16. D Make a choice： In the following multiplication facts,
which one is wrong?（ ）
（A）0.07×7=0.49
（B）4×2.4=9.6
（C）0.051×2=0.102
（D）1.2×5=60 D

17. True or False: √
0.6×9=0.9×6 （ ）

18. Problem Solving:
Grandpa does exercise every day for 0.8 hours. How many hours does he do exercise altogether for a week?
0.8×7
=8×7÷10
=56÷10
=5.6（hours）

19. Problem Solving: （2）If 1kg of cheese cost £4.59，find the cost of 3kg.
4.59×3
=459×3÷100
=1377÷100
=13.77（ pounds）