Robert is travelling on his cycle and has calculated to reach point A at 2 P.M. if he travels at 10 kmph, he will reach there at 12 noon if he travels at 15 kmph. At what speed must he travel to reach A at 1 P.M.?
8 kmph
11 kmph
12 kmph
14 kmph
Explanation:
Let the distance travelled by $ x $ km.
Then,$ \dfrac{x}{10} $-$ \dfrac{x}{15} $= 2 |
$\Rightarrow$ 3$ x $ - 2$ x $ = 60
$\Rightarrow x $ = 60 km.
Time taken to travel 60 km at 10 km/hr =$ \left(\dfrac{60}{10} \right) $hrs= 6 hrs. |
So, Robert started 6 hours before 2 P.M. i.e., at 8 A.M.
$\therefore$ Required speed =$ \left(\dfrac{60}{5} \right) $kmph.= 12 kmph. |