Guess Times Guess
A build-and-drop song about Fermi estimation — break the impossible question into pieces, guess each piece, multiply your way to an answer that's roughly right. The chorus walks the method: BREAK, GUESS, TIMES, ROUND.
How many LEAVES on that big old tree? "A MILLION!" "A ZILLION!" "Who could SEE?" Hold on — hold on — count with me — Break it apart and you'll AGREE!
How many BRANCHES? Look up — count slow — "About FIFTY!" That's a good ol' GUESS-O! How many LEAVES on ONE branch? Peek! "About a HUNDRED!" That's the trick we seek!
Fifty (TIMES!) a hundred (TIMES!) That's FIVE THOUSAND leaves! Guess times guess — ROUGH ANSWER! Roughly right — that's a WIN!
(That's a fancy word — ESS-tih-mate — break it down — approximate!)
How many BREATHS do you take in a day? "A MILLION!" "INFINITY!" the loud kids say! Hold on — hold on — break it down — Find the pieces — look around!
How many breaths in ONE minute? Try! "About TWENTY!" Good — don't be shy! Minutes in an hour? SIXTY, that's true! Hours in a day? TWENTY-FOUR for you!
Twenty (TIMES!) sixty (TIMES!) twenty-four — That's TWENTY-EIGHT THOUSAND breaths or more! Guess times guess times guess — ROUGH ANSWER! Roughly right — that's a WIN!
A man named Fermi did this trick — Asked huge questions, answered quick! "How many piano tuners in this town?" He broke it up — he wrote it down — Multiplied, and rounded too — Got an answer pretty close to true!
So when somebody says, "You'll NEVER know!" You smile and grab your pencil, GO — BREAK it apart! GUESS each part! TIMES them up! ROUND the chart!
(And sometimes the answer is TINY, you'll see —) How heavy is ONE leaf on the tree? The whole tree's pounds — DIVIDE by the count! You get a feather-light little amount!
TIMES UP for the BIG ones — DIVIDE DOWN for the small! Roughly right — roughly right — That's the handiest math of all!
Five thousand leaves on the tree, my friend — One little leaf — light as the wind! Roughly right from end to end.