看到火苗冒出来,他当机立断关掉了总开关。Kàndào huǒmiáo mào chūlái, tā dāngjīlìduàn guāndiào le zǒng kāiguān.Seeing flames flicker out, he made a split-second decision and switched off the main switch.
遇到问题要当机立断,拖得越久越麻烦。Yùdào wèntí yào dāngjīlìduàn, tuō de yuè jiǔ yuè máfan.When problems arise, act decisively; the longer you delay, the more trouble it is.
天突然下起大雨,主办方当机立断,取消了下午的活动。Tiān tūrán xià qǐ dàyǔ, zhǔbànfāng dāngjīlìduàn, qǔxiāo le xiàwǔ de huódòng.It suddenly began to pour, and the organisers decided on the spot to cancel the afternoon's event.