The bus driver drove for an hour at a speed of 100 km / h. Then he entered the motorway and increased the speed

| February 19, 2021 | education

The bus driver drove for an hour at a speed of 100 km / h. Then he entered the motorway and increased the speed by 20%. Having traveled at this speed for an hour, he felt tired and therefore reduced the speed by 20%. He drove at this speed for another 2 hours. Find the path covered by the bus in 4 hours.

t1 = 1 h.

V1 = 100 km / h.

t2 = 1 h.

V2 = V1 + 0.2 * V1.

t3 = 2 h.

V3 = V2 – 0.2 * V2.

S -?

The path of the S bus along the entire section will be the sum of the path of each section: S = S1 + S2 + S3.

Since the bus moved uniformly at each section, S1 = V1 * t1, S2 = V2 * t2 = (V1 + 0.2 * V1) t2, S3 = V3 * t3 = (V2 – 0.2 * V2) * t3 …

S1 = 100 km / h * 1 h = 100 km.

S2 = (100 km / h + 0.2 * 100 km / h) * 1 h = 120 km.

S3 = (120 km / h – 0.2 * 120 km / h) * 2 s = 192 km.

S = 100 km + 120 km + 192 km = 412 km.

Answer: the bus covered the distance S = 412 km, the bus moved for 2 hours at a speed of V3 = 96 km / h.



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