Fiora starts riding her bike at 20 mi/h. after a while, she slows down to 12 mi/h, and maintains that speed for the rest of the trip. the whole trip of 70 mi takes her 4.5 h. for what distance did she travel at 20 mi/h?

Answer : Distance, d = 40 mi.

Explanation :

It is given that,

Fiora starts riding her bike at 20 mi/h. after a while, she slows down to 12 mi/h and maintains that speed for the rest of the trip. the whole trip of 70 mi takes her 4.5 h.

Let for t hours she traveled at 20 mi/h. So, for ( 4.5 - t) h she has traveled with a speed of 12 mi/h.

We know that,

distance covered = speed × time

20 mi/h × t +12 mi/h (4.5 h - t) = 70 mi

t = 2 h

So, the distance covered in 2 h is, d = 20 mi/h × 2 h = 40 mi.

Hence, this is the required solution.

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.