Modifying css within a media query

I am using a child theme (of twentyfourteen) and am trying to remove the padding of a particular element. The code in-question appears as such in the parent style.css:

@media screen and (min-width: 846px) {
	.content-area,
	.content-sidebar {
		padding-top: 72px;
	}
}

When modify the padding to 0px thusly:

@media screen and (min-width: 846px) {
	.content-area,
	.content-sidebar {
		padding-top: 0px;
	}
}

and insert at the end of the PARENT style.css, I achieve my desired results (padding changes to 0px). However when I insert the identical code at the end of the CHILD style.css, it does nothing (the padding remains at 72px). Anyone know why this happening?