Question

Jonathan increased his rate of walking by 25% at halfway to his destination and therefore arrived half an hour earlier than was planned. How long did it take for Jonathan walk to his destination?O

Answer 1

Answer:

1.67 hours

Step-by-step explanation:

Let the original speed of Jonathan = $x$ units/hr

Let the original time taken by Jonathan = $y$ hours

Let the distance = $D$ units

Formula for distance is given as:

$Distance = Speed \times Time$

Given that half the distance is covered by original speed.

$\Rightarrow \dfrac{D}{2} = \dfrac{x}{2}\times \dfrac{y}{2}\\\Rightarrow D = \dfrac{xy}{2} ..... (1)$

Half the distance is covered by increasing the rate by 25%.

i.e. increased speed:

$\dfrac{5}{4}x\ units/hr$

Hence, Time taken:

$\dfrac{y}{2}-\dfrac{1}{2}$

Distance traveled is half of the total distance:

$\Rightarrow \dfrac{D}{2} = \dfrac{5x}{4}\times (\dfrac{y}{2}-\dfrac{1}{2})\\\Rightarrow D = \dfrac{5x}{2}\times (\dfrac{y}{2}-\dfrac{1}{2}) .... (2)$

Dividing (1) by (2):

$\dfrac{xy\times 4}{2\times 5x(y-1)} = 1\\\Rightarrow 2y=5y-5\\\Rightarrow 3y=5\\\Rightarrow y =1.67\ hours$