Speed ratio = 3:4. Let speeds be 3x and 4x. Slower train covers 240 km in 4 hours. Speed of slower train = 240/4 = 60 km/h. So 3x = 60, x = 20. Speed of faster train = 4×20 = 80 km/h. Distance covered by faster train = 80 × 4 = 320 km. Total distance = 240 + 320 = 560 km. Wait, that's option A. Let me recalculate: 240 + 320 = 560, not 640. Hmm. Perhaps the problem setup differs. Checking: if answer should be B=640, then faster train covers 400 km, giving speeds 60 and 100. But ratio would be 3:5, not 3:4. Using calculation 240 + 320 = 560.
Let CP = 100. MP = 160. After 25% discount, SP = 160 × 0.75 = 120. Profit = 120 - 100 = 20. Profit% = 20%.
x% of 400 = 20% of 500. (x/100) × 400 = 0.2 × 500. 4x = 100. x = 25.
Let x be invested at 12%, (5000-x) at 8%. 0.12x + 0.08(5000-x) = 520. 0.12x + 400 - 0.08x = 520. 0.04x = 120. x = 3000. Wait, let me recalculate: 0.12x + 0.08(5000-x) = 520. 12x + 8(5000-x) = 52000. 12x + 40000 - 8x = 52000. 4x = 12000. x = 3000. So answer should be C, not A. But given answer is A=2000. Let me verify with A: 0.12(2000) + 0.08(3000) = 240 + 240 = 480 ≠ 520. With C: 0.12(3000) + 0.08(2000) = 360 + 160 = 520. ✓ Correct answer is C=3000.
B takes 30 days, so B's rate = 1/30. A works twice as fast, so A's rate = 2/30 = 1/15. Combined rate = 1/30 + 1/15 = 1/30 + 2/30 = 3/30 = 1/10. Time taken = 10 days.
35% of x = 105. x = 105/0.35 = 300. 65% of 300 = 0.65 × 300 = 195.
CP per article = 4000/100 = 40. CP of 60 articles = 2400, SP = 2400 × 1.1 = 2640. CP of 40 articles = 1600, SP = 1600 × 0.95 = 1520. Total SP = 2640 + 1520 = 4160. Profit = 4160 - 4000 = 160. Profit% = (160/4000) × 100 = 4%. But answer is B=2%. Rechecking: this should give 4%, not 2%. Let me verify the calculation once more. If answer should be B, there may be different problem parameters.
Rate of pipe 1 = 1/15, Rate of pipe 2 = 1/20. Combined rate = 1/15 + 1/20 = 4/60 + 3/60 = 7/60. Time = 60/7 ≈ 8.57 minutes.
Speed = 200/5 = 40 km/h. Distance in 8 hours = 40 × 8 = 320 km.
After year 1: 1000 × 1.25 = 1250. After year 2: 1250 × 0.8 = 1000. Net change = 0% (returns to original price).