Sum of 4 numbers = 35 × 4 = 140. Sum of 3 numbers = 28 + 36 + 42 = 106. Fourth number = 140 - 106 = 34.
Total distance = 200 + 150 = 350 km. Total time = 4 + 2.5 = 6.5 hours. Average speed = 350/6.5 = 53.85 ≈ 54 km/h. Recalculate: 350/6.5 = 3500/65 = 700/13 ≈ 53.85. Closest is 50. Let me verify: if average is 50, total = 50 × 6.5 = 325 ≠ 350. If 55: 55 × 6.5 = 357.5. Hmm, answer should be ~54 but closest option is 55.
Downstream speed = 45/3 = 15 km/h. Upstream speed = 35/5 = 7 km/h. Speed in still water = (15 + 7)/2 = 11 km/h. Wait, that's option D. Let me recheck: (D+U)/2 = (15+7)/2 = 11. But the question asks for average speed accounting for distances. Total distance = 45+35 = 80. Total time = 3+5 = 8. Average = 80/8 = 10 km/h.
Initial average age × 6 = Total. New average = (Initial average + 2). Change in total = 6 × 2 = 12. New person's age = 40 + 12 = 52 years.
SI on first = 8000 × 10 × 3 / 100 = 2400. SI on second = 6000 × 12 × 2 / 100 = 1440. Total SI = 3840. Total capital = 14000. Average rate = (3840 / 14000) × 100 = 27.43% over period. For annual: 3840 / (14000 × average years) where years = (8000×3 + 6000×2)/14000 = 36000/14000 = 2.57 years. Rate = 3840/(14000×2.57) ≈ 10.6%. Closest option is 10.5%.
Rate of worker 1 = 1/8, worker 2 = 1/12. Combined rate = 1/8 + 1/12 = (3+2)/24 = 5/24. Time = 24/5 = 4.8 days.
CP = 100 × 50 = 5000. SP of 60 at 20% profit = 60 × 50 × 1.2 = 3600. SP of 40 at 10% loss = 40 × 50 × 0.9 = 1800. Total SP = 5400. Profit = 400. Profit% = (400/5000) × 100 = 8%.
Total height of 5 = 165 × 5 = 825 cm. After adding 180 cm: 825 + 180 = 1005 cm. New average = 1005 / 6 = 167.5 cm.
For equal distances, average speed = 3/(1/40 + 1/50 + 1/60) = 3/((3+2.4+2)/120) = 3/(7.4/120) = 360/7.4 = 48.65 ≈ 49.09 km/h. Using LCD: 3/((15+12+10)/600) = 1800/37 ≈ 48.65 km/h.
For 8 consecutive even numbers with average 15: Let smallest = x. Numbers are x, x+2, x+4, ..., x+14. Average = (x + x+14)/2 = x+7 = 15. So x = 8. But average of even numbers can't be odd. Question error - assuming average is 14: x+7 = 14, x = 7 (odd). If average is 16: x+7 = 16, x = 9 (odd). Reconsidering: average of 8 numbers = 15 means sum = 120. If x is smallest: x + (x+2) + ... + (x+14) = 8x + 56 = 120. So 8x = 64, x = 8. But 8 is option D. Verification: 8,10,12,14,16,18,20,22 average = 136/8 = 17 ≠ 15. Problem has inconsistency. Likely intended average = 9: 8x + 56 = 72, x = 2.