Thinking of solving problems: In practical problems, division is generally used when the keyword is average, multiplication is generally used when multiple is used, addition and subtraction are generally used when the ratio is more or less, and formulas are applied according to keywords.

Problem solving process:

3× 1.3=3.9

A: 1 kg 3 is 3.9 yuan money.

Extended Data # Vertical Calculation-Calculation Result: First, align the last digit of two multipliers, then use the second multipliers respectively, multiply each digit by one multiplier in turn from the last digit, and finally accumulate the calculation result into a product. If the multiplier is decimal, the corresponding multiple can be expanded first, and then the product can be reduced by the corresponding multiple;

Problem solving process:

Step 1: 3×3=9

Step 2: 1×3=30

According to the above calculation steps, the comprehensive result is 3.9.

If in doubt, please ask questions. If satisfied, please adopt them.