Plant flowers in a trapezoidal flower field with an upper base of 30 meters, a lower base of 40 meters, and a height of 15 meters, and apply 300 grams of fertilizer per square meter. How many kilograms of fertilizer does this flower field need to fertilize in total?
在一块上底是30米、下底是40米、高是15米的梯形花田里种植鲜花，每平方米施肥300克．这块花田一共需要施肥多少千克？
<gadget id="calculator">30 + 40</gadget>
<output>70</output>

<gadget id="calculator">15 / 2</gadget>
<output>15/2 = around 7.5</output>

<gadget id="calculator">300 / 1_000</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">70 * (15/2) * (3/10)</gadget>
<output>315/2 = around 157.5</output>

<result>315/2 = around 157.5</result>