Reduce / Increase Image Size : Linux Command

Command To Reduce Image Size By x%
command :
convert -resize x% source.jpg new.jpg
For example :
to reduce size by 20% of image source.jpg
convert -resize 20% source.jpg new.jpg
target image new.jpg is 20% less of size

Command To Increase Size Image By x%
command :
convert -resize x% source.jpg new.jpg
For example :
to increase size by 120% of image "source.jpg"
convert -resize 120% source.jpg new.jpg
target "image new.jpg" is 120% more of size