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The speed of a car is about 80 km / h. It takes five hours to go from place a to place B and four hours to return. What's the speed of return?
80 * 5 △ 4 = speed of return
From land a to land B, the ratio of the distance traveled and the distance not traveled is 3:4. If you travel another 80 kilometers, the ratio of the distance traveled and the distance not traveled is 5:4
How many kilometers is the distance between the two places?
Solving problems with invariants
The total distance remains unchanged:
Done: not done = 3:4 = 27:36
Done: not done = 5:4 = 35:28
Each piece: 80 ÷ (35-27) = 10 (km)
Distance between the two places: 10x (27 + 36) = 630 (km)
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