Question

Add the following
$7$ minutes $15$ seconds and $5$ minutes $35$ seconds._________

Answer 1

$7$ minutes $15$ seconds $=7\times 60+15$ sec $=435$ sec

$5$ minutes $35$ seconds $=5\times 60+35$ sec $=335$ sec

Adding $7$ minutes $15$ sec from $5$ minutes $35$ seconds gives $435+335=770$ sec $=12\times 60+50=12$ min $50$ sec