Question

A student walks 8 km at v km/h. She then cycles 15 km at 2v km/h. In terms of , solve the time taken in hours
a) When walking
b) when cycling
c) If the total time for the journey is 2 h 35 min, find the girl's walking speed.

Answer 1

$\huge\star\underline\blue {Answer:-}$

Given

Distance travelled by walking, d1= 8km

Speed while walking = v km/h

Distance covered by cycling = 15 km

Speed while cycling = 2v km/h

we know

$speed = \frac{distance}{time} \\ time = \frac{distance}{speed}$

a)Walking:-

$time = \frac{8}{v} hrs$

b)Cycling:-

$time = \frac{15}{2v} hrs$

c)total time:-

$total \: time = t1 + t2 \\ = \frac{8}{v} + \frac{15}{2v} \\ = \frac{16 + 15}{2v} \\ = \frac{31}{2v} hrs$

Given time=2hrs35min=2+35/60hrs=155/60=31/12hrs

Hence

$\frac{31}{2v} = \frac{31}{12} \\ 2v = 12 \\ v = 6 \frac{km}{h}$

Hence Girl's Walking speed is 6km/h

Hope it helps! ! ! !

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Regards,

Abhinay.