Acyclist croses a 30 metre long bridge in 3 1/4 minutes. find the speed of the cyclist?

3 1/4 minutes = 189 seconds

30 / 189 = .0086

The cyclist was going .0086 feet per second if I calculated correctly.

We know, Speed = Distance / time
Here, d = 30 m
t = 3 1/4 min = 13/4 min. = 13/4 * 60 = 195 sec

Substitute their value, 
s = 30 / 195
s = 6/39 m/s

In short, Your Answer would be 6/39 or 0.153 m/s
[ Your Units might be different so be careful with that ]

Hope this helps!

21 is the answer the answer is 21