Question

A jet flew from Tokyo to Bangkok, a distance of $200$ km. On the return trip the speed was decreased by $50$ km/h. If the difference in the times of the flights was $2$ hour. How much time will the flight take from Bangkok to Tokyo?

• A. $1$ hour
• B. $2$ hours
• C. $3$ hours
• D. $4$ hours

Answer 1

The correct option is D $4$ hours

Time $=$ $\frac{distance}{speed}$
Let the going time, $t=\frac{200}{x}$
Return time: $t+2=\frac{200}{x-50}$
$\frac{200}{x}$ $+2=$ $\frac{200}{x-50}$
$200x-10000+2x^2-100x=200x$
On factoring we get,
$(x+50)(x-100)=0$
$x=100$ (neglecting the negative value of $x$)
Return time: $t+2=$ $\frac{200}{x-50}$
$x=100$
$\Rightarrow t=4$ hours