It takes 3 hour 15 minutes to fly from city a to city b at constant speed. Find how long the journey takes if
A) the speed is 1×1÷2 times of the original speed and
B) if the speed is three-quarters of the original speed.

Respuesta :

Answer:

a) t= 2hours and 10 minutes

b) t=4hours and 20 minutes

v1t1=v2t2

Answer:

Step-by-step explanation:

rate = distance / time     distance is constant (a-b) so call it D

time = distance / rate      rate = speed (ie miles per hour = mph)

time = distance / speed      

A)  if the new speed is 1.5 of the original speed    

     original time = 3.25 hours  or 195 minutes

  3.25  = D / 1       new time = D/1.5       find new time

         3.25 is to D   as    new time is to  D/1.5

            3.25/D = new time / D/1.5                   multiple D/1.5 on both sides

            (3.25/D) ( D/1.5)      = new time           the distance D cancels

            3.25 (D / D) / 1.5   = new time

            3.25 / 1.5  = 2.167 hours   or 2 hours and 10 minutes

B)   if the speed is 3/4 the original speed

original time = 3.25 hours  or 195 minutes

  3.25  = D / 1       new time = D/(3/4)       find new time

         3.25 is to D   as    new time is to  D/0.75

            3.25/D = new time / D/0.75                       multiple D/0.75 on both sides

            (3.25/D) ( D/0.75)      = new time

            3.25 (D / D) / 0.75     = new time

            3.25 / 0.75  = 4.333 hours   or 4 hours and 20 minutes