know how many beans make five

Verb

know how many beans make five (third-person singular simple present knows how many beans make five, present participle knowing how many beans make five, simple past knew how many beans make five, past participle known how many beans make five)

1. (idiomatic) To be knowledgeable about how the world works; to have common sense and judgement.
   • They got the best prices, and he could assure the House that they knew how many beans made five, and how many shillings were in a pound, just as well as the Europeans.1894, New Zealand Parliament, Parliamentary Debates: House of Representatives
   • […] no composer or dramatic poet has ever pretended to be able to perform all the parts he writes for the singers, actors and players who are his executants. One might as well expect Napoleon to be a fencer, or the Astronomer Royal to know how many beans make five any better than his bookkeeper.1987, Bernard Shaw, Back to Methuselah