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7. A train which is 100 meters long is traveling at a speed of 90 km per hour. How many
seconds will it take for this train to pass completely through a 300 meter tunnel?
A 4
B 8
C 12
D 16
E 20

The answer is D, 16. How do you get 16 tho?

Respuesta :

Answer:

D; 16 seconds

Step-by-step explanation:

speed = distance/time

speed = 90 km/hr

We need to convert this to m/s because the tunnel is in meters and the time is in seconds:

[tex]\frac{90km}{hr} * \frac{1hr}{3600s} *\frac{1000m}{1km} =25m/s[/tex]

distance = 300 m (tunnel) + 100 m (train) = 400 meters

Solving for time:

[tex]25m/s=\frac{400m}{t} \\(25m/s)(t)=400m\\t=\frac{400m}{25m/s} \\t=16 s[/tex]

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