let's call your speed "a"
her walking speed is then "2a"
and her friend's scooter speed is 10 a
let's also call the distance you need to walk "d"
so the time (t)you need is:
d/t=a
t=d/a
and her time is:
t=[tex] \frac{d}{2} /2a+ \frac{d}{2} /10a[/tex]
(half a distance with the speed of 2a and half a distance (d/2) with the distance of 10 a
now we count (we know that her time is 30 minutes)
30= [tex] \frac{d}{4a}+\frac{d}{20a}[/tex] //multiply by 20a
600a= [tex] 5d+d[/tex]
600a=6d/divide by 6
100a=d
Now, in order to calculate your time we need to calculate:
t=d/a
but we know how much is d now!
t=[tex] \frac{100a}{a} [/tex]=100
which means that you need 100 minutes, or 1 h 40 minutes!!!
