Question 493492
Speed=distance/time
S=Speed=?
D=Distance=1mile
Time=4minutes
Changing minutes into hours
60minutes =1hour
Divide by 60 both sides
60 Minutes/60 =1/60hour
1minute=1/60 hour
1minute=0.01666666666 hour
Multiply by 4 both sides
4*1minute=4*(0.01666666666) hour
4minutes=0.06666666664 hour
Speed=mile/hour
Speed=1/0.06666666664
Speed=15.00000006 miles/hour
Or approximately = 15 miles/hour

OR
2nd method

She covers 1 mile in…………………..4 minutes

Multiply by 15 both sides 
(reason for multiplying by 15 is we want to change minutes into hour)

She covers (1*15) mile in…………………..4*15 minutes
She covers 15 miles in…………………..60 minutes (or an hour)

Her speed will be 15 miles/hour