At 09 20, Roshel left Town J and cycled towards Town K. Irene left Town J and cycled towards Town K at 09 50. Irene's cycling speed was 4 km/h faster than Roshel. At 12 20, Irene caught up with Roshel. Find the cycling speed of each cyclist.

1. Roshel
2. Irene

(a)
Duration that Irene cycled from 09 50 to 12 20
= 2³⁰₆₀
= 2¹₂ h

Distance that Irene cycled more than Roshel
= 2¹₂ x 4
= 10 km

However, since Roshel left 30 minutes earlier than Irene and Irene caught up with Roshel, it means that Roshel has cycled 10 km in 30 min.

1 h = 60 min 
30 min = 30 ÷ 60 = ¹₂ h

Roshel's cycling speed
= 10 ÷ ¹₂
= 10 x ²₁
= 20 km/h

(b)
Irene's cycling speed
= 20 + 4
= 24 km/h

Answer(s): (a) 20 km/h ; (b) 24 km/h