There is a two-plate balance with only one weight of 5 grams and one weight of 30 grams. Now it is necessary to divide 300 grams of salt into 3 equal parts. Ask how many times the balance needs to be weighed at least.
有一架两盘天平，只有5克和30克砝码各一个，现在要把300克盐分成3等份，问最少需要用天平称多少次．
<result>3</result>