An athlete training for a cross-country race covered three types of terrain in three distinct segments of a practice run; she ran across stretches of packed dirt, rocky scree, and grass, in that order. On packed dirt, she ran at an average speed of 201 meters per minute; she then rapidly slowed on the rocky scree and covered the grass segment at an average speed of 100.5 meters per minute. The distance she covered on grass was four times the distance she covered on packed dirt, and it took her 21 minutes to cover both.On the table, select the distance she covered on both these terrains, in meters. Make only two selections, one in each column.
Solution: Let's assume
Average speed on packed dirt as x meters/min
Average speed on grass as y meters/min
Distance covered on packed dirt as d1 meters
Distance covered on grass as d2 meters
Time taken to cover packed dirt as t1 minutes
Time taken to cover grass as t2 minutes
Given that,x = 201 meters/min
y = 100.5 meters/min
d2 = 4d1
t1 + t2 = 21 ------- (1)
Now, t1 = \(\frac{d1}{x}\)
t1 = \(\frac{d1}{201}\)
Similarly, t2 = \(\frac{d2}{y}\)
t2 = \(\frac{4d1}{100.5}\)
t2 = \(\frac{8d1}{201}\)
From (1)
\(\frac{d1}{201}\) + \(\frac{8d1}{201}\) = 21
\(\frac{9d1}{201}\) = 21
d1 = \(\frac{21 * 201}{9}\)
d1 = 469 meters
and d2 = 4 * 469 meters = 1876 meters
Distance covered on packed dirt = 469 metersDistance covered on grass = 1876 meters
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