The cyclist, having driven 4 km at a speed of 12 km / h, stopped and rested for 40 minutes.

| February 23, 2021 | education

The cyclist, having driven 4 km at a speed of 12 km / h, stopped and rested for 40 minutes. He drove the remaining 8 km of the way at a speed of 8 km / h. Find the average speed of the cyclist.

To calculate the value of the average speed of the specified cyclist, you must use the formula: Vav = (Sн + Sк) / (tн + tо + tк) = (Sн + Sk) / (Sн / Vн + to + Sк / Vк).

Values of variables: Sн – the initial part of the cyclist’s path (Sн = 4 km); Sk is the remaining path (Sk = 8 km); Vн – initial speed (Vн = 12 km / h); to – duration of rest (to = 40 min = 2/3 h); Vк – final speed (Vк = 8 km / h).

Calculation: Vav = (Sn + Sk) / (Sn / Vn + to + Sk / Vk) = (4 + 8) / (4/12 + 2/3 + 8/8) = 6 km / h.

Answer: The average ground speed of this cyclist is 6 km / h.



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