Question

Jules is training for a marathon. She finds that for the first 5 km of her training run, she runs
at a constant speed of x km/h. For the remaining 7 km of her training run, her speed reduces
by 5 km/h. Write an algebraic expression for the total time Jules takes to run 12 km. Recall
that s t
d = .

Answer 1

x * t1 = 5
(x-5) *t2 = 7
so
t1 = 5/x
t2 = 7 / (x-5)
total time = t = 5/x + 7/(x-5)
= 5 (x-5) /(x^2-5x) + 7x / (x^2 - 5x)
= (12x - 25) / (x^2 -5x)