1. **Estimate and evaluate simple additions and subtractions:** - a) Estimate $20.1 + 2.1 \approx 20 + 2 = 22$. - Evaluate exactly: $20.1 + 2.1 = 22.2$. - b) Estimate $77.8 + 3.2 \approx 78 + 3 = 81$. - Evaluate exactly: $77.8 + 3.2 = 81.0$. - c) Estimate $16.4 - 5.5 \approx 16 - 6 = 10$. - Evaluate exactly: $16.4 - 5.5 = 10.9$. - d) Estimate $66.02 - 12.11 \approx 66 - 12 = 54$. - Evaluate exactly: $66.02 - 12.11 = 53.91$. 2. **Estimate and evaluate sums and differences with three terms:** - a) Estimate $13.9 + 3.42 + 1.08 \approx 14 + 3 + 1 = 18$. - Evaluate exactly: $13.9 + 3.42 + 1.08 = 18.4$. - b) Estimate $123.4 + 30.2 + 2 \approx 123 + 30 + 2 = 155$. - Evaluate exactly: $123.4 + 30.2 + 2 = 155.6$. - c) Estimate $165.27 - 38.9 - 57.3 \approx 165 - 39 - 57 = 69$. - Evaluate exactly: $165.27 - 38.9 - 57.3 = 69.07$. - d) Estimate $79.154 - 3.857 - 12.24 \approx 79 - 4 - 12 = 63$. - Evaluate exactly: $79.154 - 3.857 - 12.24 = 63.057$. 3. **Estimate and evaluate multiplications and divisions:** - a) Estimate $149.37 \times 2 \approx 150 \times 2 = 300$. - Evaluate exactly: $149.37 \times 2 = 298.74$. - b) Estimate $28.34 \times 7 \approx 28 \times 7 = 196$. - Evaluate exactly: $28.34 \times 7 = 198.38$. - c) Estimate $9.876 \times 4 \approx 10 \times 4 = 40$. - Evaluate exactly: $9.876 \times 4 = 39.504$. - d) Estimate $4.9 \div 2 \approx 5 \div 2 = 2.5$. - Evaluate exactly: $4.9 \div 2 = 2.45$. - e) Estimate $20.6 \div 6 \approx 21 \div 6 = 3.5$. - Evaluate exactly: $20.6 \div 6 \approx 3.4333$. - f) Estimate $42.3 \div 62 \approx 42 \div 62 \approx 0.68$. - Evaluate exactly: $42.3 \div 62 \approx 0.6823$. 4. **Estimate and evaluate expressions with brackets:** - a) Estimate $484.7 + 200.18 - 50.6 \approx 485 + 200 - 51 = 634$. - Evaluate exactly: $484.7 + 200.18 - 50.6 = 634.28$. - b) Estimate $194.2 - (3.8 - 8.51) \approx 194 - (-5) = 199$. - Evaluate exactly: $194.2 - (3.8 - 8.51) = 194.2 - (-4.71) = 198.91$. - c) Estimate $-3.15 - (1.79 + 34.7) \approx -3 - 36 = -39$. - Evaluate exactly: $-3.15 - (1.79 + 34.7) = -3.15 - 36.49 = -39.64$. - d) Estimate $(14.99 + 36.17) - (3.98 + 5.49) \approx (15 + 36) - (4 + 5) = 51 - 9 = 42$. - Evaluate exactly: $(14.99 + 36.17) - (3.98 + 5.49) = 51.16 - 9.47 = 41.69$. 5. **Context-based question: Ali's lunch cost** - Ali bought Seafood fried rice for $3.50 and Tom Yum soup for $2.50. - Total cost = $3.50 + 2.50 = 6.00$. **Final answers:** 1a) 22.2 1b) 81.0 1c) 10.9 1d) 53.91 2a) 18.4 2b) 155.6 2c) 69.07 2d) 63.057 3a) 298.74 3b) 198.38 3c) 39.504 3d) 2.45 3e) 3.4333 3f) 0.6823 4a) 634.28 4b) 198.91 4c) -39.64 4d) 41.69 5) 6.00