A leather factory produces a batch of leather shoes. In April, (1/7) of these leather shoes are completed. In May, more (1/7) is produced than in April. The total production in two months is exactly 1500 pairs. How many pairs of this batch of leather shoes are there?
某皮革厂生产一批皮鞋，四月份完成这批皮鞋的(1/7)，五月份比四月份多生产(1/7)，两个月生产的总数正好是1500双．这批皮鞋共有多少双？
<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">1 + (1/7)</gadget>
<output>8/7 = around 1.142857</output>

<gadget id="calculator">(1/7) * (8/7)</gadget>
<output>8/49 = around 0.163265</output>

<gadget id="calculator">(1/7) + (8/49)</gadget>
<output>15/49 = around 0.306122</output>

<gadget id="calculator">1_500 / (15/49)</gadget>
<output>4_900</output>

<result>4_900</result>