In Michael Johnson's world$-$record $400m$ sprint, he ran the first $100m$ in $11\mathrm{.}20s$; then he reached the $200m$ mark after a total time of $21\mathrm{.}32s$ had elapsed, reached the $300m$ mark after $31\mathrm{.}76s,$ and finished in $43\mathrm{.}18s.$