VTMO 2014 — Grade 6 — semifinal Question 4

Question 4

Sawing $a = 72 \,\mathrm{cm}$ bar into $6 \,\mathrm{cm}$ pieces takes $165$ minutes. How long for $a = 144 \,\mathrm{cm}$ bar with the same piece length?

$300$
$315$
$330$
$345$
$360$