Gujarati
4-2.Quadratic Equations and Inequations
hard

A man standing on a railway platform noticed that a train took $21\, s$ to cross the platform (this means the time elapsed from the moment the engine enters the platform till the last compartment leaves the platform) which is $88\,m$ long, and that it took $9 s$ to pass him. Assuming that the train was moving with uniform speed, what is the length of the train in meters?

A

$55$

B

$60$

C

$66$

D

$72$

(KVPY-2015)

Solution

(c)

Let the length of trains be $x$ meter.

Time taken by train $h$ cross person $=9\,s$

$\therefore$ Speed of trains $=\frac{x}{9} m / s$

Time taken by train to cross platform $=21\,s$

$\therefore \frac{x}{9}=\frac{x+88}{21}$

${[\because \text { length of plateform }=88\,m ]}$

$\Rightarrow 21 x=9 x+9 \times 88$

$\Rightarrow 12 x=9 \times 88$

$\Rightarrow x=\frac{9 \times 88}{12}=66\,m$

Standard 11
Mathematics

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