For the construction of green trees in the new countryside, Zhangjia Village purchased a batch of saplings. The survival rate of these saplings is 70%-80%. To ensure the survival of 2800 saplings, how many saplings should be planted at least.
新农村建设绿树造林，张家村购进一批树苗，这批树苗的成活率在70%-80%，要保证成活2800棵树苗，最少要栽多少棵树苗．
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">2_800 / (4/5)</gadget>
<output>3_500</output>

<result>3_500</result>