Explanation
This is a mnemonic to help you remember the units of measurement in the metric system. Take the first letter of each word: Kids Hate Doing Math During Cloudy Mondays → K-H-D-M-D-C-M, standing for Km Hm Dam M Dm Cm Mm (Kilometer, Hectometer, Dekameter, Meter, Decimeter, Centimeter, Millimeter).
Additional Note
it also helps when converting (e.g., meters to millimeters), count how many spaces there are from meters to millimeters to know where to place the decimal.