90 students went to the seaside to play, and the class leader bought pure water for the students, each with a bottle of 2 yuan. The store offers buy four get one free, please do the math, how much will the squad leader pay in total?
90名同学到海边游玩，班长给同学们买纯净水，每人一瓶，每瓶2元．商店优惠买四送一，请你算一算，班长一共要付多少钱？
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<gadget id="calculator">90 / 5</gadget>
<output>18</output>

<gadget id="calculator">18 * 4 * 2</gadget>
<output>144</output>

<result>144</result>