30. Find the area of the square field if a train
800 metres long passes the field with a speed of
120 kmph in one minute,
(A) 1.44 sq.km
(B) 4 sq.km
(C) 2 sq.km
(D) 2.64 sq.km
Answers
Answer:
SOLUTION : 1.44 sq. km
120 km/hr = 120 * 5/18 = 33.33 m/s
v = d/t ; 33.33 = d/60
d = 2000 m
Hence, in one minute the train travels 2000 m. But, as the train is 800 m long and it passes the field, the length of the field is 2000 – 800 = 1200 m.
Area = 1200 * 1200 = 1.44 sq. km
Step-by-step explanation:
Answer:
The correct answer is 2.64 sq.km.
Step-by-step explanation:
From the above question,
They have given :
Based on the given information, the correct answer is (D) 2.64 sq.km. The area of the square field can be calculated by the formula:
area = length × width.
Since the train's length is 800 metres and the speed is 120 kmph, which equals to 33.33 metres per second, the length of the field can be calculated by:
length = 33.33 m/s × 1 min
= 33.33 m × 60 s
= 2000 m
Thus, the area of the square field will be equal to 2000 m × 2000
m = 4000000
m2 = 4 sq.km
m2 = 2.64 sq.km.
In this case, the distance is 800 meters, the speed is 120 km/hr (which is equivalent to 120 x 5/18 meters/second), and the time is 60 seconds (since the train takes 1 minute to cross the field).
So, substituting these values into the formula, we have:
800 = (120 x 5/18) x time
Solving for time, we get:
time = 800 / (120 x 5/18)
= 800 / (25/3)
= 800 x 3 / 25
= 96 seconds.
Since the train moves in a straight line, and the field is square, the length of the side of the square is the same as the distance the train covers in 96 seconds, which is 800 meters.
Therefore, the area of the square field is the square of the length of one side, which is:
800 x 800 = 640000 square meters
= 64 hectares
= 2.56 square kilometers.
Hence,
The correct answer is 2.64 sq.km.
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