Centimetre and metre কী?

Example 7.8 (Which unit for which job?)

Small things like a beetle, a stamp or your hand are measured in centimetres. Big things like a corridor, a bus or a swimming pool are measured in metres: the pool is $25\,\mathrm{m}$ long — imagine counting that in fingernail-widths! Choosing a sensible unit is half the work of measuring.

Example 7.9 (Estimate, then check)

Before measuring, players guess: how long is the kitchen table? Papa says $2\,\mathrm{m}$, Lina says $1\,\mathrm{m}$ and a bit. Then the metre stick decides: $1\,\mathrm{m}$ and almost a half — point for Lina. Guessing first trains your eye; measuring keeps everyone honest.