# Help to solve please a problem (program of the 6th class): The motor ship passed distance from Paragraph A in In across the current for 4 h 30 min., and from In in And against the current for 6 h 18 min. What own speed of the boat if the speed of a watercourse is equal to 2.4 km/h?

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Let own speed of the boat (boat speed) be equal in still water - x km/h, then its speed on a current x + 2.4, and speed against the current x - 2.4. Let S - distance between Paragraphs A and B. Time of the movement on a current of 4 h 30 min. = 4.5 h, time of the movement against the current: 6 h are 18 min. old = 6.3 Parts 4.5 = S: (x + 2.4) (1) 6.3 = S: (x - 2.4) (2) Of (1) S = 4.5 · (x +2.4) (3) we Will substitute (3) in (2) 6.3 = 4.5 · (x +2.4): (x - 2.4) 7 · (x - 2.4) = 5 · (x +2.4) the 7th - = 5x + 12 of the 2nd = 28.8 x = 14.4 (km/h) is 16.8 the own speed of the boat. From (3) S = 4.5 · (14.4 +2.4) = 4.5 · 16.8 = 75.6 (km) of Answer: 75.6 kmpust own speed of the motor ship = X, then speed on a current of X +2.4. and against the current X - 2.4. It passed across the current 4.5 (X +2.4) km, and against the current - - 6.3(X-2.4) of km. But since the distance between points is identical, we will work out the equation: 4.5 (X + 2.4) = 6.3 (X-2.4) 4.5X + 10.8 = 6,3H-15,12 4,5X - 6,3X = - 10.8 - 15.12 - 1.8X = - 25.92 X = 14.4 Answer: 14.4km/hour - own speed of the motor ship
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