Let's see what to do buddy.....
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[tex]Acceleration = 4 \: \: \frac{mile}{ h } p( min ) [/tex]
Thus ;
The speed increases 4 units per minute.
The train has a speed of 25 mph now.
After a minute it has a speed of 29 mph.
After a minute it has a speed of 33 mph.
After a minute it has a speed of 37 mph.
Look ; 4 units per minute means 4 units per 60 seconds, thus the speed increases 1 unit per 15 seconds .
If the speed wants to increasing from 37 to 40 , needs 3 × 15 seconds = 45 sec.
So we have : 1 min + 1 min + 1 min + 45 sec .
3 minutes and 45 seconds or 225 seconds need to the speed increasing from 25 mph to 40 mph.
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And we're done.....♥️♥️♥️♥️♥️