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Ji-Hun and Kana are running a marathon. Due to the volume of people running, the starts occur in waves. Kana starts at 9:35 a.m. and runs at an average rate of 7 miles per hour. Ji-Hun starts at 10:00 a.m. and runs at an average rate of 8 mph. Assuming constant paces and no stops, in how many miles will Ji-Hun catch up to Kana?

Respuesta :

Answer:

23.52 miles

Step-by-step explanation:

Let us find the number of miles that they would have run.

Kana starts at 9:35 a.m. and runs at an average rate of 7 mph.

Let the time she has spent so far be t.

Speed is given as:

s = d / t

where d = distance and t = time

=> d = s * t

Therefore, for Kana:

d = 7 * t = 7t _____________(1)

Ji-Hun starts at 10:00 am (25 minutes after Hannah) and runs at an average rate of 8 mph.

25 minutes = 25/60 hour = 0.42 hour

So, his time (compared to Kana's) is t - 0.42.

therefore, for Ji-Hun:

d = 8 * (t - 0.42)

=> d = 8t - 3.36 ____________(2)

Equating (1) and (2):

7t = 8t - 3.36

=> 8t - 7t = 3.36

t = 3.36 hours

Therefore, let us find d:

d = 7 * 3.36 = 23.52 miles

So, Ji-Hun will catch up to Kana after 23.52 miles.

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