If I needed to install Apache Bench, the binary for which is ab
I would run: 

yum provides ab

This returns: 

Loading mirror speeds from cached hostfile
 * base: mirrors.clouvider.net
 * epel: epel.mirrors.ovh.net
 * extras: centos.serverspace.co.uk
 * updates: mirror.sov.uk.goscomb.net
httpd-tools-2.4.6-45.el7.centos.x86_64 : Tools for use with the Apache HTTP Server
Repo        : base
Matched from:
Filename    : /usr/bin/ab

Therefore the package needed is httpd-tools (sudo yum install http-tools)