The simplest form of the ratio $1.5 : 2.5$ is

### Concept & Simplifying Decimal Ratios Ratios should ideally be expressed as fractions consisting of whole numbers in their lowest terms. Decimal ratios can be simplified by multiplying by powers of 10 to clear the decimals, then dividing by the greatest common divisor. ### Step-by-Step Solution * **Given:** Ratio is $1.5 : 2.5$. * **Eliminate decimals:** Multiply both sides of the ratio by $10$ to remove the single decimal place. $(1.5 \times 10) : (2.5 \times 10) = 15 : 25$ * **Simplify:** Find the highest common factor (HCF) of $15$ and $25$, which is $5$. Divide both sides by $5$. $\frac{15}{5} : \frac{25}{5} = 3 : 5$ ### Exam Strategy & Shortcut You can mentally shift the decimal point one place to the right for both numbers to get $15 : 25$. Recognize immediately that both end in $5$, making them divisible by $5$. $15/5 = 3$ and $25/5 = 5$, giving $3 : 5$. ### Common Pitfall Selecting an option that is mathematically equivalent but not in the *simplest* form. For example, $15 : 25$ and $6 : 10$ are equivalent ratios, but $3 : 5$ is the most reduced, simplest form requested by the question. ### Final Answer Therefore, the correct answer is **$3 : 5$**.