Question

Sam covers 40% of a certain distance at 40km/hr and the remaining distance at 30 km/hr .What is the average speed ?
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Answer 1

Answer:

I can't understand the question

Answer 2

Answer:

$33 \frac{1}{3} kmh {}^{ - 1}$

Step-by-step explanation:

Let the total distance covered by Sam be 'x'

So the distance covered at 40 km/h = 40% of x

= 40/100 ×x

= 10x/25 km

Time taken to cover this distance

$= \frac{ \frac{10x}{25} }{40}$

$= \frac{10x}{25} \times \frac{1}{40}$

$= \frac{x}{100} hours$

Again, distance covered at 30km/h= x - 10x/25

= 25x - 10x/25

= 15x/25

$time \: taken \: to \: covered \: this \: distance \: = \frac{ \frac{15x}{25} }{30}$

$= \frac{15x}{25} \times \frac{1}{30}$

$= \frac{x}{50} hours$

$hence \: total \: time \: taken \: = \frac{x}{100} + \frac{x}{50}$

$= \frac{x + 2x}{100}$

$= \frac{3x}{100} hours$

$so \: the \: avg \: speed = \frac{x}{ \frac{3x}{100} }$

$= x \times \frac{100}{3x}$

$= \frac{100}{3} kmh {}^{ - 1}$

$i.e \: 33 \frac{1}{3} kmh {}^{ - 1}$