Maths question:

Victor 跑步速度是他步行速步的兩倍。當佢跑了 2 小時之後步行了 3 小時後，佢經過了 21 公里。請問他的步行速度是多少？

Let his walking speed = x km/hr
then his running speed = 2x km/hr

2(2x) + 3(x) = 21
4x + 3x = 21
x = 3

Therefore his walking speed is 3 km/hr.

the best one..

Let a be the walking speed

3 hours walking + 2 hours running = 21 km

3 x a + 2 x (2 x a) = 21 km

3a + 4a = 21km

7a = 21 km

Victor's walking speed = 21/7 km = 3 km per hour

X係行o既speed
咁run就係2x

run左2個鐘即係2乖2x=4x
行左3個鐘即係3乖x=3x
搞左咁3個鐘之後,,,,travelled左21km..
即係4x+3x=21km
7x=21km
x=3km

強烈建議下次問問題記得講唔該..
同問之前先查查字典

Let his walking speed be y km/h,then his running speed is 2y km/h.
2(2y)+3y=21
4y+3y=21
7y=21
y=3
Therefore his walking speed is 3km/h.