VTMO 2026 - Grade 7 - Semifinal - SET 3 - Self-study Question 18

Question 18

A digital clock displays the time of day in HH:MM:SS format from 00:00:00 to 23:59:59. How many times in $24$ hours do all six digits change after one second?

Question illustration

$1$
$2$
$3$
$12$
$24$