Final answer:
Chi should first perform the subtraction within the parentheses (operation 2) in the expression (1.25 - 0.4) / 7 × 3. Next, she should do the division by 7 (operation 4), and finally, multiply the result by 3 (operation 3), following the PEMDAS order.
Step-by-step explanation:
The expression Chi needs to simplify is (1.25 - 0.4) / 7 × 3. According to the order of operations, commonly known as PEMDAS which stands for Parentheses, Exponents, Multiplication and Division (from left to right), and Addition and Subtraction (from left to right), Chi should perform the operations in this specific order. Starting with the Parentheses (P), Chi should first execute the subtraction (1.25 minus 0.4) which is operation 2). Following the subtraction within the parentheses, she should then attend to the division (operation 4), dividing by 7, and finish with multiplication (operation 3), multiplying by 3.
It is essential to note that when using a calculator, the answer might give more decimal places than the data with the least significant figures. As per the significant figures rules for multiplication and division, the final answer should be rounded to match the significant figures of the datum with the least amount.
In regard to simplifying expressions, the correct use of significant figures ensures that the final answer is reported with the proper precision. When simplifying using standard arithmetic or a calculator, it is necessary to be attentive to rounding and maintaining the appropriate level of precision in the calculation.