Simplification and Approximation

15.5% of 323 ≈ 0.155 × 323 = 50.065. 20.8% of 198 ≈ 0.208 × 198 = 41.184. The difference is 50.065 - 41.184 = 8.881, which rounds to 9. Option E (9) is the closest approximate value.

3058 ÷ 27 = 113.26 (since 27 × 113 = 3051). Then 113.26 × 3 = 339.78, which rounds to 340. This matches option C exactly.

(3.6)² × (1.75)² = (3.6 × 1.75)² = (6.3)² ≈ 39.69, which rounds to 40. Alternatively: 12.96 × 3.0625 ≈ 39.69. Option B is correct.

68% of 1388 ≈ 0.68 × 1390 ≈ 945. 26% of 624 ≈ 0.26 × 625 ≈ 162.5. 945 + 162.5 - 115 = 1107.5 - 115 = 992.5 ≈ 990. Option C (990) is correct.

Round to nearest convenient numbers: 375.25 ≈ 375, 4.985 ≈ 5. Then 375 × 5 = 1875. To verify precision: 375.25 × 4.985 ≈ 375 × 5 - small adjustments. The actual product is very close to 1875. Option C (1875) is correct and is the closest approximation among the options.

Given: 1³ + 2³ + ... + 9³ = 2025. Required sum: (0.11)³ + (0.22)³ + ... + (0.99)³ = 0.11³(1³ + 2³ + ... + 9³) = 0.001331 × 2025 ≈ 2.695. Option B is correct.

Round 9654 ÷ 21 to 460 (21 × 460 = 9660, very close to 9654). Round 7638 ÷ 44 to 174 (44 × 174 = 7656, close to 7638). Adding: 460 + 174 = 634. Among options, 630 is closest to 634.

Calculate step by step: 564 + 82 = 646, then 646 - 44 = 602, then 602 - 34 = 568. The final result is 568, which does not match any of the given options (284, 350, 160, 142). Therefore, 'None of these' is the correct answer.

First simplify the numerator: 2198 - 1347 - 403 = 448. Then simplify the denominator: 159 - 113 - 27 = 19. Divide: 448 ÷ 19 ≈ 23.58, which rounds to approximately 24. The question asks for an approximate value, so 24 is the closest correct option.

Approximate 73.99% as 74% and 9.98% as 10%. Then 74% of 1299 ≈ 0.74 × 1299 ≈ 961.26, and 10% of 1899 ≈ 189.9. Adding these gives 1151.16, which rounds to 1150. Option A (1250) would result from using 75% instead of 74%.

Calculate stepwise: 732.86 - 153.72 = 579.14; then 579.14 - 83.006 = 496.134; finally 496.134 + 103.04 = 599.174. The closest approximation is 600.

Approximating: 48.23% ≈ 50%, 50% of 124 = 62. 12.4% ≈ 12%, 12% of 482.3 = 57.876. Sum = 62 + 57.876 = 119.876 ≈ 117. The approximation method yields 117 as the closest answer.

Approximate: 7854.49 × 0.75 ≈ 7854 × 3/4 ≈ 5891. 3654.98 × 59.876 ≈ 3655 × 60 ≈ 219300. Total ≈ 5891 + 219300 = 225191. Option C (225200) is closest. The question asks for approximate value.

Approximating: 70% of 870 = 609, 40% of 86 = 34.4. So 609 = ? - 34.4 - 73, which gives ? = 609 + 34.4 + 73 = 716.4. The closest option is C (720). Rearrange: ? = 69.89% of 870 + 39.8% of 85.80 + 72.98.

Approximating: 63 × 9450 ÷ 248 = 594,900 ÷ 248 ≈ 2,398.8. The calculation uses rounding to nearest whole numbers for practical approximation. 63.2172 ≈ 63, 9449.23 ≈ 9450, 248.0034 ≈ 248. The result rounds to approximately 2400, making option A correct.