If the car travels from point A to point B at a speed of 80 km / h, it will be 20 minutes late

| April 19, 2021 | education

If the car travels from point A to point B at a speed of 80 km / h, it will be 20 minutes late, and if it travels at a speed of 90 km / h, it will arrive 10 minutes earlier. Find the distance between points A and B.

We have: 20 minutes = (20/60) hours = ⅓ hours; 10 minutes = (10/60) hours = 1/6 hour.
Let S denote the distance between points A and B.
If the speed of the car is 80 km / h, then it will arrive from point A to point B in (S / 80) hours. At the same time, it will be ⅓ hour late.
If the car’s speed is 90 km / h, then it will arrive from point A to point B in (S / 90) = hours. At the same time, he will arrive 1/6 hour earlier.
By the condition of the problem (S / 80) – ⅓ = (S / 90) + 1/6 or 9 * S – 8 * S = 120 + 240, whence S = 360 km.
Answer: 360 km



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