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# SBT Toán lớp 5 trang 8,9,10,11: Ôn tập: Phép nhân và phép chia hai

## Introduction

In this article, we will review the concepts of multiplication and division of fractions in grade 5 mathematics. We will cover various exercises from the textbook and provide step-by-step solutions. By the end of this article, you will have a better understanding of these mathematical operations.

## Exercise 1: Multiplication of Fractions

Let’s begin with the exercise on page 8 of the grade 5 mathematics textbook. Solve the following multiplication problems:

a) 25×37; 47×34; 49×310; 2×518.

b) 38:75; 34:910; 78:2; 6:23.

c) 13×35×59; 1516:38×34.

Solution:

a) To solve 25×37, we multiply the numerators (25×37) and the denominators (1×1). The result is 635.

For 47×34, we can break down the calculation into smaller steps. First, we multiply the numerators (4×37) and the denominators (1×4). The result is 148. Then, we multiply 148 by the remaining numerator 4. The final result is 592.

Similarly, for 49×310, we multiply the numerators (4×39×10) and the denominators (1×1×2). The result is 215.

Finally, for 2×518, we multiply the numerators (2×52×9) and the denominators (1×1). The result is 59.

b) To solve 38:75, we multiply the numerators (38×57) and the denominators (1×5). The result is 1556.

For 34:910, we multiply the numerators (3×104×9) and the denominators (1×1). The result is 56.

Similarly, for 78:2, we multiply the numerators (7×16) and the denominators (1×2). The result is 716.

Finally, for 6:23, we multiply the numerators (6×32) and the denominators (1×1). The result is 182.

c) To solve 13×35×59, we multiply the numerators (1×3×53×5×9) and the denominators (1×1×1×1×1). The result is 19.

For 1516:38×34, we multiply the numerators (15×8×38×2×3×4) and the denominators (1×1×1×1). The result is 158.

## Exercise 2: Division of Fractions

Let’s move on to the exercise on page 9 of the grade 5 mathematics textbook. Solve the following division problems:

a) 35×827×53.

b) 719×13+719×23.

Solution:

a) To solve 35×827×53, we multiply the numerators (35×53×827) and the denominators (1×1). The result is 827.

b) For 719×13+719×23, we calculate the multiplication first. The result is 719×1=719.

## Exercise 3: Word Problems

In exercise 34 on page 9 of the grade 5 mathematics textbook, we have word problems that involve multiplication and division of fractions. Let’s solve them together:

a) x×12=13.

b) x:45=52.

c) 29:x=23.

Solution:

a) To solve x×12=13, we divide both sides of the equation by 12. The result is x=13:12=23.

For x:45=52, we multiply both sides by 45. The result is x=52×45=2.

Similarly, for 29:x=23, we multiply both sides by x. The result is x=29:23=13.

## Exercise 4: Area Calculation

Moving on to exercise 35 on page 9 of the grade 5 mathematics textbook, we will calculate the area of a rectangular glass.

A rectangular glass has a length of 45 and a width of 12. Let’s calculate its area.

Solution:

The area of the rectangular glass is given by the formula length × width. So, 45×12=540.

Therefore, the area of the glass is 540 square units.

## Exercise 5: Real-life Problem

In exercise 36 on page 9 of the grade 5 mathematics textbook, we have a real-life problem involving mixing and measuring liquids. Let’s solve it together:

We mix 12 liters of grape juice with 74 liters of water to make grape juice. Each cup can hold 14 liters of juice. How many cups of grape juice can we pour?

Solution:

To find the total volume of the grape juice, we add 12 liters of grape juice to 74 liters of water. The result is 12+74=86 liters.

Next, we divide the total volume by the capacity of each cup, which is 14 liters. So, 86:14=6.

Therefore, we can pour 6 cups of grape juice.

## Conclusion

In this article, we reviewed the concepts of multiplication and division of fractions in grade 5 mathematics. We solved various exercises from the textbook, providing step-by-step solutions. Remember to practice these concepts regularly to enhance your mathematical skills. For more detailed solutions and additional exercises, visit Kienthucykhoa.com.

Keep up the good work, and happy learning!

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