Let the distance between his house and park be 100 meters. Let us assume he takes 30 min daily. Hence his speed would be 100/30.
One day, if he wishes to save 1/3rd
of 30 minutes, that is 10 minutes, he should cover the distance in 20 minutes in which case his speed would be 100/20.
Required increment in speed =
Percentage of increase in speed = (Required increment in speed/original speed) x 100)% =