Question
There are 21 poles with a constant distance between each pole. A car takes 30 seconds to reach the 16th pole. How long does it take to reach the last pole?
Answer: Option B
THE FIRST POLE IS CROSSED AT THE ZEROTH SECOND. THE TIMER STARTS AFTER THE CAR CROSSES THE FIRST POLE. LET THE DISTANCE BETWEEN EACH POLE BE X M. TO REACH THE 16TH POLE, THE DISTANCE TRAVELLED BY THE CAR IS 15X. THE SPEED OF THE CAR IS 15X/30 = X/2 M/S TO REACH THE 21ST POLE, IT HAS TO TRAVEL A DISTANCE OF 20X. TIME TAKEN
= 20X÷(X/2)
= 40 SECONDS
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THE FIRST POLE IS CROSSED AT THE ZEROTH SECOND. THE TIMER STARTS AFTER THE CAR CROSSES THE FIRST POLE. LET THE DISTANCE BETWEEN EACH POLE BE X M. TO REACH THE 16TH POLE, THE DISTANCE TRAVELLED BY THE CAR IS 15X. THE SPEED OF THE CAR IS 15X/30 = X/2 M/S TO REACH THE 21ST POLE, IT HAS TO TRAVEL A DISTANCE OF 20X. TIME TAKEN
= 20X÷(X/2)
= 40 SECONDS
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