There are several fourth-grade contestants in the "World Olympics", among which the average weight of boys is 43 kg, and the average weight of girls is 34 kg. It is known that the number of boys in the fourth-grade contestants is twice the number of girls. So, what is the average weight of all the competitors in the fourth grade in kilograms?
"世奥赛"四年级参赛选手有若干名，其中男生的平均体重是43千克，女生的平均体重是34千克，已知四年级参赛选手中男生人数是女生人数的2倍．那么，四年级全体参赛选手的平均体重是多少千克？
<gadget id="calculator">43 * 2</gadget>
<output>86</output>

<gadget id="calculator">86 + 34</gadget>
<output>120</output>

<gadget id="calculator">2 + 1</gadget>
<output>3</output>

<gadget id="calculator">120 / 3</gadget>
<output>40</output>

<result>40</result>