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Monday, April 30, 2007
MATH QUESTION OF THE DAY
A train of length l, traveling at a constant velocity, passes a pole in t seconds. If the same train traveling at the same velocity passes a platform in 3t seconds, then the length of the platform is (A) 0.5l (B) l (C) 1.5l (D) 2l (E) 3l
The distance traveled by the train while passing the pole is l (which is the length of the train). The train takes t seconds to pass the pole. Recall the formula velocity = distance/time. Applying this formula, we get velocity =l/t While passing the platform, the train travels a distance of l + x, where x is the length of the platform. The train takes 3t seconds at the velocity of l/t to cross the platform. Recalling the formula distance = velocity × time and substituting the values for the respective variables, we get [l + x] =[l/t]× 3t by substitution l + x = 3l by canceling t x = 2l by subtracting l from both sides Hence, the length of the platform is 2l. The answer is (D).
explain
ReplyDeleteexplain buddies....
ReplyDeleteD - If it takes t secs to pass l length of train and if takes 3t secs to pass l lenght of train.. it means that the length of platform is 2l...
ReplyDeletei.e. 2l(platform)+l(train length) = 3t secs.
hope it is correct. scrap me if anything wrong
The distance traveled by the train while passing the pole is l (which is the length of the train). The
ReplyDeletetrain takes t seconds to pass the pole. Recall the formula velocity = distance/time. Applying this formula,
we get
velocity =l/t
While passing the platform, the train travels a distance of l + x, where x is the length of the platform. The
train takes 3t seconds at the velocity of l/t to cross the platform. Recalling the formula distance =
velocity × time and substituting the values for the respective variables, we get
[l + x] =[l/t]× 3t
by substitution
l + x = 3l by canceling t
x = 2l by subtracting l from both sides
Hence, the length of the platform is 2l. The answer is (D).