Xiaohong measured the temperature 4 times in one day, which were 15°C, 27°C, 25°C, and 21°C. What is the average temperature of the day in °C.
小红在一天中测量了4次气温，分别是15℃、27℃、25℃、21℃．这一天的平均气温是多少℃．
<gadget id="calculator">15 + 27 + 25 + 21</gadget>
<output>88</output>

<gadget id="calculator">88 / 4</gadget>
<output>22</output>

<result>22</result>