maths world problem

Question

(a) Anna drives 45km to work each day.One day she drives the first 25km at an average speed of 82 km/h.

She takes 36 minutes to drive the remaining distance.

Calculate her average speed, in km/h, for the whole journey.

(b) Anna’s journey home is 47km, correct to the nearest kilometre.

One day her journey home takes 65 minutes, correct to the nearest 5 minutes.

Calculate the upper bound of her average speed, in km/h, for the journey home.

(c) The probability that Anna arrives at work on time or early on any given day is 5/8

Calculate the probability that she is late on both Monday and Tuesday.

Give your answer as a fraction.

thank you very much to those who answered. very appreciate it.

Answer 1

25 km at 82 km/hr

d=rt distance = rate of speed times time

time = distance/rate of speed

t =d/r =

42/60 = 25/r

for the 1st 25 km

last 20km

36/60 = 20/(a different r)

average r = 45/(42/60 + 36/60) = 45/(78/60) 45(60)/78= 34.6 km/hr

first 25 km, r = 60(25)/42 = 35.7 km/hr

last 20 km r= 20(60)/36 = 1200/36 = 33 1/3 km/hr