answer (one's) purpose
To be useful for a particular task. If that's the only paintbrush we have, I think it will answer my purpose.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
answer someone's purposeand serve someone's purpose
to fit or suit someone's aim or goal. This piece of wood will answer my purpose quite nicely. The new car serves our purpose perfectly.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.