Find the fraction of a number

### 1.1. Knowledge to remember

**Problem : **A basket of oranges has 12 oranges. Ask \(\frac{2}{3}\) how many oranges are in the basket ?

*Comment : *

a) \(\frac{1}{3}\) the number of oranges in the basket is : \(12:3 = 4\) (fruit)

\(\frac{2}{3}\) the number of oranges in the basket is : \(4 \times 2 = 8\) (fruit)

b) We can find \(\frac{2}{3}\) the number of oranges in the basket as follows:

\(12 \times \frac{2}{3} = 8\) (fruit)

*Solution*

\(\frac{2}{3}\) the number of oranges in the basket is :

\(12 \times \frac{2}{3} = 8\) (fruit)

Answer: 8 oranges.

**Want to find? **\(\frac{2}{3}\)** of 12, we multiply 12 by **\(\frac{2}{3}\)**. **

### 1.2. Solving Textbook Exercises

**Lesson 1: **A class has 35 students, in which \(\frac{3}{5}\) the number of students is classified as good. Calculate the number of students with good grades in that class.

**Solution guide:**

- Finding the number of students with good grades means that we find \(\frac{3}{5}\) of 35 students. To find \(\frac{3}{5}\) of 35 students, we multiply \(\frac{3}{5}\) by 35, then add units to the result.

*Solution*

The number of students with good grades in that class is:

\(35 \times \frac{3}{5} = 21 (student)

Answer: 21 students.

**Lesson 2:** A rectangular schoolyard has a length of 120m and a width equal to \(\frac{5}{6}\) length. Calculate the width of the school yard?

__Solution guide:__

- Finding the width of the school yard means we find \(\frac{5}{6}\) of 120m. To find \(\frac{5}{6}\) of 120m we multiply 120 times \(\frac{5}{6}\), then add units to the result.

*Solution*

The width of the field is:

\(120 \times \frac{5}{6} = 100\) (m)

Answer: 100m.

**Lesson 3:** Class 4A has 16 boys and the number of girls is equal to \(\frac{9}{8}\) the number of boys. How many girls are there in class 4A?

__Solution guide:__

Finding the number of female students means that we find \(\frac{9}{8}\) of 16 students. To find the \(\frac{9}{8}\) of 16 students, multiply 16 by \(\frac{9}{8}\), then add units to the result.

*Solution*

The number of girls in class 4A is:

\(16 \times \frac{9}{8} = 18\) (student)

Answer: 18 students.

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