Lesson 4-5
Let's study the division of fractions by natural numbers.
| A cook had two bags of sugar, with |
3 |
kilogram of sugar in each bag. Using an equal amount every day, |
| 5 |
| the cook used up all the sugar in five days. How much sugar did the cook use each day? |
| Let's see how to do the calculation |
3 |
× 2 ÷ 5. |
| 5 |
| 3 |
× 2 ÷ 5 |
= |
3 |
× 2 × |
1 |
| 5 |
5 |
5 |
| |
| |
= |
3 × 2 × 1 |
| 5 × 5 |
| |
| |
= |
6 |
| 25 |
| How can we do the calculation 2 |
1 |
× 3 ÷ 14? |
| 3 |
| 2 |
1 |
× 3 ÷ 14 |
= |
|
7 |
× |
3 ÷ 14 |
| 3 |
3 |
| |
| |
= |
|
7 |
× |
3 |
| 3 |
14 |
| |
| |
1 |
|
1 |
| |
= |
|
7 |
× |
3 |
| 3 |
14 |
| |
1 |
|
2 |
| |
| |
= |
1 |
| 2 |
Fill in the spaces with the correct numbers.
Evaluate the following expressions.
| 4 |
× 3 ÷ 9 |
|
3 |
1 |
× 3 ÷ 4 |
| 7 |
2 |
| How can we do the calculation, |
3 |
÷ 5 × 3 ? |
| 4 |
| 3 |
÷ 5 × 3 |
= |
3 |
× |
1 |
× 3 |
| 4 |
4 |
5 |
| |
| |
= |
3 × 1 × 3 |
| 4 × 5 |
| |
| |
= |
9 |
| 20 |
| Let’s see how to calculate 1 |
2 |
÷ 5 × 6. |
| 3 |
| |
1 |
|
2 |
| 1 |
2 |
÷ 5 × 6 |
= |
|
5 |
× |
1 |
× |
6 |
|
| 3 |
3 |
5 |
| |
1 |
|
1 |
| |
| |
= |
2 |
Fill in the spaces with the correct numbers.
Evaluate the following expressions and mixed calculations.
| 1 |
3 |
÷ 7 × 8 |
|
3 |
1 |
÷ 8 × 2 |
| 4 |
3 |
| Mr. Joggerst divided 2 |
2 |
liters of juice equally among four bottles. His children drank all the |
| 7 |
| juice from three of the bottles. How much juice did the children drink? |
| How can we do the calculation, |
3 |
÷ 4 ÷ 2 ? |
| 5 |
| 3 |
÷ 4 ÷ 2 |
= |
3 |
× |
1 |
× |
1 |
| 5 |
5 |
4 |
2 |
| |
| |
= |
3 × 1 × 1 |
| 5 × 4 × 2 |
| |
| |
= |
3 |
| 40 |
| How can we do the calculation, 6 |
1 |
÷ 5 ÷ 5 ? |
| 4 |
| |
1 |
| |
5 |
| 6 |
1 |
÷ 5 ÷ 5 |
= |
|
|
25 |
× |
1 |
× |
1 |
| 4 |
4 |
5 |
5 |
| |
| |
= |
1 |
| 4 |
Fill in the spaces with the correct numbers.
Evaluate the following expressions and mixed calculations.
| 3 |
1 |
÷ 6 ÷ 7 |
|
4 |
2 |
÷ 4 ÷ 3 |
| 2 |
3 |
| 10 |
2 |
÷ 3 ÷ 4 |
|
3 |
6 |
÷ 2 ÷ 9 |
| 5 |
7 |
| A family had 3 |
3 |
kilograms of beef, which they divided into three equal parts. If five people share one of the |
| 4 |
| parts equally, what is the weight of each person’s portion? |
