Math 2 Lesson: Liters

### 1.1. Knowledge to remember

The pitcher holds more water than the cup.

The cup holds less water than the pitcher.

Pour milk to fill the shift, we get 1 liter of milk.

Abbreviated liter is

### 1.2. Math forms

**Form 1: Read and write the number of liters**

– Read numbers and add liter units.

– Write numbers: Write the number and add the unit of liter denoted by l to the end.

**Form 2: Calculate**

– Perform calculations with numbers

– Write the unit of liters in the result.

(Add and subtract numbers when the same unit of measure is liters)

**Form 3: How many liters are left?**

To calculate the number of liters remaining after being reduced, you need to subtract the original number of liters from the number of liters poured out.

**Form 4: Math Quiz**

– Read and analyze the topic.

– Find a solution to the problem: Pay attention to the keywords “remaining”; “all”… to use reasonable calculation.

– Present the solution.

– Check the answer you just found.

### 1.3. Solve textbook exercises pages 41, 42

**Lesson 1**

Reading and writing:

__Solution method__

Read and write the given numbers.

Applying knowledge: “l” is read as liters.

__Solution guide__

**Lesson 2**

Calculation (according to the form):

a) 9l + 8l = 17l 15l + 5l = 2l + 2l + 6l =

b) 17l – 6l = 18l – 5l = 28l – 4l – 2l =

__Solution method__

Do the calculation with the numbers and then write the unit of liters after the result you find.

__Solution guide__

a) 9l + 8l = 17l 15l + 5l = 20l 2l + 2l + 6l = 10l

b) 17l – 6l = 11l 18l – 5l = 13l 28l – 4l – 2l = 22l

**lesson 3**

How many liters are left?

a)

__Solution method__

Take the number of liters in the can minus the number of liters poured.

__Solution guide__

b) 10l – 2l = 8l

c) 20l – 10l = 10l.

Lesson 4

The first time the store sold 12 liters of fish sauce, the next time it sold 15 liters of fish sauce. How many liters of fish sauce were sold both times?

__Solution method__

To find the number of liters of fish sauce sold both times, we take the number of liters of fish sauce sold in the first time plus the number of liters of fish sauce sold in the next time.

__Solution guide__

The number of liters of fish sauce both times the store sold is

12 + 15 = 27 (l)

Answer: 27 liters.

### 1.4. Textbook exercise solution page 43

**Lesson 1**

Calculate:

2l + 1l = 15l – 5l = 3l + 2l – 1l =

16l + 5l = 35l – 12l = 16l – 4l + 15l =

__Solution method__

Do the calculation with the numbers and then write the unit of liters after the result.

__Solution guide__

2l + 1l= 3l 15l – 5l = 10l 3l + 2l – 1l = 4l

16l + 5l = 21l 35l – 12l = 23l 16l – 4l + 15l = 27l

**Lesson 2**

Number?

__Solution method__

Sum the numbers given in each figure and fill in the blanks with the result.

__Solution guide__

a) 1l + 2l + 3l = 6l; b) 3l + 5l = 8l; c) 10l + 20l = 30l.

**lesson 3**

The first tank has 16 liters of oil, the second one has 2 liters less oil than the first one. How many liters of oil are in the second barrel?

__Solution method__

**Summary**

First barrel: 16l

The second barrel is less than the first one: 2l

Second barrel: … liters?

**The answer**

To find how many liters of oil in the second barrel, subtract 2 liters of oil from the number of liters of oil in the first barrel.

__Solution guide__

The second barrel has the number of liters of oil:

16 – 2 = 14 (l)

Answer: 14l.

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