Question

Write numbers from $1$ to $15$. What fraction of them are prime numbers?

Answer 1

Step 1: Write the prime numbers from $1$ to $15$

The prime numbers are numbers that can be divided exactly by themselves and $1$.

The prime numbers from $1$ to $15$ are $2$, $3$, $5$, $7$, $11$ and $13$.

Step 2: Write the fraction of prime numbers from $1$ to $15$

A fraction that represents a part of a whole is written as: $\frac{\mathrm{The}\mathrm{number}\mathrm{of}\mathrm{parts}\mathrm{taken}\mathrm{out}}{\mathrm{The}\mathrm{total}\mathrm{number}\mathrm{of}\mathrm{parts}}$

The number of prime numbers from $1$ to $15$ $=6$

The total numbers from $1$ to $15$ $=15$

The required fraction $=\frac{6}{15}$

$\frac{6}{15}$ can be simplified as: $\frac{6÷3}{15÷3}=\frac{2}{5}$

Hence, the fraction of prime numbers from $1$ to $15$ is $\frac{2}{5}$.