$3.5$ can be expressed in terms of percentage as

### Concept & Formula To convert a decimal number to a percentage, you must multiply the number by 100 and add the percentage sign (%). $$ \text{Percentage} = \left( \text{Decimal} \times 100 \right)\% $$ ### Step-by-Step Solution * **Given:** The decimal number is $3.5$. * **Calculation:** Multiply the given number by 100. $$ 3.5 \times 100 $$ * Shift the decimal point two places to the right: $$ = 350\% $$ ### Exam Strategy & Shortcut Remember that the whole number $1$ represents $100\%$. Therefore, $3$ represents $300\%$. By basic logic, the number $3.5$ must clearly be $350\%$. This can be done instantly by observation without writing anything down. ### Common Pitfall Mistaking the decimal itself as the percentage (choosing $3.5\%$) or shifting the decimal in the wrong direction to get $0.35\%$. Always remember the fundamental rule: "Decimal to Percent = Multiply by 100". ### Final Answer **Therefore, the correct answer is 350%.**