A barrel of oil is 50 kilograms, 2/5 of it is used for the first time, and 15 kilograms is used for the second time, what fraction of this barrel of oil is shared between the two times?
一桶油50千克，第一次用去它的(2/5)，第二次用去15千克，两次共用去这桶油的几分之几？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">15 / 50</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">(2/5) + (3/10)</gadget>
<output>7/10 = around 0.7</output>

<result>7/10 = around 0.7</result>