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A truck carries 15 tonnes of rigid packets, each at least 0.5 tonne, against a suitable headboard supporting the top packets by at least 150 mm. What minimum combined rated strength must the two tie downs provide?
卡車載有共15噸、每包至少0.5噸的剛性貨物，緊靠合適前擋板，頂層有至少150毫米受支撐。兩條捆綁裝置的合計額定強度至少是多少？
The 15-tonne rigid-packet load needs combined rated lashing strength of at least 15 tonnes when a suitable headboard supports the top packets by at least 150 mm.
頂層貨物有至少150毫米受合適前擋板支撐時，15噸剛性貨物的捆綁裝置合計額定強度至少15噸。
閱讀相關知識
Each packet must weigh at least 0.5 tonne. You cannot apply this one-times requirement if only the lower packets are supported and top-packet support is less than 150 mm.
本題按每包至少0.5噸且符合支撐條件計算；只有下層受支撐而頂層不足150毫米時，不能套用1倍要求。