1. Note that the number 1.8 consists of two parts 1 and 0.8.
2. The decimal 0.8 can be written as the fraction \(\dfrac{8}{10}.\)
3. Add these two numbers:
\(1+\dfrac{8}{10}=\dfrac{10}{10}+\dfrac{8}{10}=\dfrac{10+8}{10}=\dfrac{18}{10}.\)
4. Since 18=2·3·3 and 10=2·5, the fraction \(\dfrac{18}{10}\) can be simplified to the rational number
\(\dfrac{18}{10}=\dfrac{2\cdot 3\cdot 3}{2\cdot 5}=\dfrac{3\cdot 3}{5}=\dfrac{9}{5}.\)
