1. **Problem statement:** We need to round numbers to specified decimal places and perform approximate calculations by rounding to whole numbers. 2. **Rounding rules:** - To round to two decimals, look at the third decimal digit: if 5 or more, round up the second decimal digit. - To round to three decimals, look at the fourth decimal digit: if 5 or more, round up the third decimal digit. - For rounding to whole numbers, look at the first decimal digit: if 5 or more, round up the integer. 3. **Rounding to two decimals:** - a) $12.409 \approx 12.41$ (since the third decimal 9 is >5, round up) - b) $0.0019 \approx 0.00$ (third decimal is 1, less than 5, so stays 0) 4. **Rounding to three decimals:** - b) $1.5894 \approx 1.590$ (fourth decimal 4 < 5, so third decimal stays 9) - b) $0.9089 \approx 0.909$ (fourth decimal 9 > 5, round up third decimal 8 to 9) 5. **Approximate calculations by rounding to whole numbers:** - a) $4.9 \cdot 10.2 \approx 5 \cdot 10 = 50$ - b) $62.1 \cdot 3.3 \approx 62 \cdot 3 = 186$ - c) $12.1 : 5.3 \approx 12 : 5 = 2.4$ - d) $4.7 : 0.9 \approx 5 : 1 = 5$ **Final answers:** - a) 12.41 - b) 0.00 - b) 1.590 - b) 0.909 - a) 50 - b) 186 - c) 2.4 - d) 5 This completes the rounding and approximate calculations as requested.