Question

Amit travelled from A to B at an average speed 80
km/hr. He travelled the first 75% of the distance in
two third of the time and the rest at a constant speed
of x km/h. The value of x is​

Answer 1

value of x = 60 km/hr

Step-by-step explanation:

Let say Distance Traveled = 4D km

& Time Taken  = 3T hr

Speed = Distance / time = 80

=> 4D/3T = 80

=> D = 60T

first 75% of the distance = (75/100)4D = 3D  km

two third of the time = (2/3)3T = 2T

Speed = 3D/2T  = 3 * 60T /2T = 90 km/hr

Remaining Distance = 3D - 2D = D km

Remaining time = 3T - 2T = T hr

Speed = x = D/T  => 60T/T = 60

value of x = 60 km/hr

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Answer 2

Answer:

The value of x would be 60.

Step-by-step explanation:

Let total distance = D km,

And, total time taken = t hours,

So, the average speed = $\frac{Distance}{Time}$ = $\frac{D}{t}$ km/h,

Average speed of the entire journey = 80 km/h

$\implies \frac{D}{t}=80-----(1)$

Now, 2/3rd of total time = $\frac{2}{3}t$

Remaining time = $t-\frac{2}{3}t$

$=\frac{3t-2t}{3}$

$= \frac{t}{3}$

Also, 75% of the total distance = $\frac{75D}{100}$ = $\frac{3}{4}D$ km,

So, the remaining distance = $D-\frac{3}{4}D$ = $\frac{1}{4}D$ km,

Thus, the speed in remaining 25% of the journey = $\frac{D/4}{t/3}$

$=\frac{3D}{4t}\text{ km per hour}$

According to the question,

$x=\frac{3D}{4t}$

From equation (1),

$x = \frac{3}{4}\times 80=3\times 20=60$

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