In order to prevent and control the H7N9 bird flu, the school made a potion of "84" disinfectant and water at a ratio of 1:100, and disinfected the activity venue with spray every day. There are 3 bottles of "84" disinfectant, each bottle is 500ml, how many liters do you need to add water?
为开展对H7N9禽流感的防控工作，学校把"84"消毒液和水按1：100配成药水，每天对活动场地用喷雾消毒．现有3瓶"84"消毒液，每瓶500毫升，需兑水多少升？
<gadget id="calculator">100 / 1_000</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">500 * 3 * (1/10)</gadget>
<output>150</output>

<result>150</result>