"To triple that number" means to multiply a given number by three.
Sentences with «to triple that number»
These promotions can offer bonuses and earn you double and triple the number of miles and points you'd normally earn. (theglobetrottingteacher.com)
The number of fast food and casual chains that received passing grades this year was triple the number in 2015, the first year of the report. (consumerreports.org)