How many seconds are in a $24$ hour day?

Compare hours, minutes, and seconds:

The units in which time is measured are seconds, minutes, and hours.

$1$ minute = $60$ seconds

$1$ hour = $60$ minutes

$1$ day = $24$ hours

Now, $1$ hour = $60\times 60=3600$ seconds

$1$ day = $3600\times 24=86400$ seconds

Hence, in a $24$ hour day, there are $86400$ seconds.