A regular hexagonal nursery is divided into many equal regular triangles by straight lines parallel to the edge of the nursery, and saplings are planted on the vertices of the triangles. It is known that 90 trees are planted in the outermost circle of the nursery. Question: How many saplings are planted in the nursery?
一个正六边形的苗圃，用平行干苗圃边缘的直线把它分成许多相等的正三角形，在三角形的顶点上都栽种树苗，已知苗圃的最外面一圈栽有90棵．问：苗圃中共栽树苗多少棵？
<gadget id="calculator">90 * 8</gadget>
<output>720</output>

<gadget id="calculator">720 + 1</gadget>
<output>721</output>

<result>721</result>