tolong jawab y, soalnya ga ngerti. tp yg betul y

1.]
v = 72 km/jam = 20 m/s
s = 1 km = 1000 m

t = _ ?

t = s / v
t = 1000 / 20
t = 50 s

2.]
s₁ = 150 km
t₁ = 1,5 jam
s₂ = 90 km

t₂ = _ ?


s₁ : t₁ = s₂ : t₂
150 : 1,5 = 90 : t₂
100 = 90 : t₂
t₂ = 0,9 jam