A whale weighs 40 kg at birth, and then increases by 30 kg every year. How much does the whale weigh after 15 years?
鲸鱼出生时重40千克，以后每年增长30千克，15年后鲸鱼重多少千克．
<gadget id="calculator">30 * 15</gadget>
<output>450</output>

<gadget id="calculator">450 + 40</gadget>
<output>490</output>

<result>490</result>