A truck drove out from city A to city B. After 1.2 hours from point A to point B, the bus left after 0.8 hours

| May 6, 2021 | education

A truck drove out from city A to city B. After 1.2 hours from point A to point B, the bus left after 0.8 hours, it lagged behind the car by 24 km. Find the speed of the bus if it is known that it is more than the speed of the truck by 30 km / h.

1. The bus speed is equal to: Va km / h;

2. Truck speed: Vm km / h;

3. By the condition of the problem: Va = (Vm + 30) km / h;

4. The bus left after the car at: To = 1.2 hours;

5. Distance of removal of the truck: So = Vm * To km;

6. Bus travel time: Td = 0.8 hours;

7. Distance between bus and car: Sd = 24 km;

8. Equation of motion:

Sd = Sm – Sa;

Sd = (So + Vm * Td) – Va * Td;

Sd = Vm * (To + Td) – Va * Td;

24 = Vm * (1.2 + o, 8) – (Vm + 30) * 0.8;

2 * Vm – 0.8 * Vm – 24 = 24;

1.2 * Vm = 48;

Vm = 48 / 1.2 = 40 km / h;

Va = Vm + 30 = 40 + 30 = 70 km / h.

Answer: the bus speed is 70 km / h.



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