When Xiao Ming walks 10km an hour from home to school, he will arrive at school 10 minutes later than planned, and walk 15km an hour, Now Xiao Ming wants to get to school five minutes earlier than he planned, but he doesn't know how many kilometers he should walk per hour. Can you tell Xiao Ming what his speed is?

When Xiao Ming walks 10km an hour from home to school, he will arrive at school 10 minutes later than planned, and walk 15km an hour, Now Xiao Ming wants to get to school five minutes earlier than he planned, but he doesn't know how many kilometers he should walk per hour. Can you tell Xiao Ming what his speed is?

Suppose Xiaoming plans to walk to school in X minutes
10（X+10）=15（X-10）
10X+100=15X-150
15X-10X=100+150
5X=250
X=50
So, Xiao Ming wants to get to school five minutes earlier than he planned. Every minute he should walk: 10 × (50 + 10) / (50-5) = 13 and 1 / 3 (km)

If Xiao Ming walks 10km an hour from home to school, he will arrive at school 10 minutes later than the planned time; if he walks 15km an hour, he will arrive at school 10 minutes earlier than the planned time. Now Xiao Ming wants to arrive at school 5 minutes earlier than the planned time, but he doesn't know how many km he should walk per hour. Can you tell Xiao Ming what his speed is?

Assuming that the distance from home to school is s km, the equation: S10 − 16 = S15 + 16, the solution is s = 10km, so t = 1010 × 60-10 = 50 minutes. Assuming that he has to ride at least x km per hour, 10x × 60 = 50-5, the solution is x = 403 km. A: he has to ride at least 403 km per hour