two tains of equal lengths take 10 seconds and 15 seconds respectively to cross a telegraph post. if the length of each train be 100 metres, in what time ( in seconds ) will they cross each other travelling in opposite direction? Select the correct option.
A) 12 B) 11.9 C) 16 D) 20 E) 18
<gadget id="calculator">100 + 100</gadget>
<output>200</output>

<gadget id="calculator">100 / 15</gadget>
<output>20/3 = around 6.666667</output>

<gadget id="calculator">100 / 10</gadget>
<output>10</output>

<gadget id="calculator">(20/3) + 10</gadget>
<output>50/3 = around 16.666667</output>

<gadget id="calculator">200 / (50/3)</gadget>
<output>12</output>

<result>B</result>
two tains of equal lengths take 10 seconds and 15 seconds respectively to cross a telegraph post. if the length of each train be 100 metres, in what time ( in seconds ) will they cross each other travelling in opposite direction?
divide(add(100, 100), add(divide(100, 15), divide(100, 10)))
sol . speed of the first train = [ 100 / 10 ] m / sec = 10 m / sec . speed of the second train = [ 100 / 15 ] m / sec = 6.7 m / sec . relative speed = ( 10 + 6.7 ) = m / sec = 16.7 m / sec . ∴ required time = ( 100 + 100 ) / 16.7 secc = 11.9 sec . answer b