他总是丢三落四，经常找不到东西。

Tā zǒngshì diūsān làsì, jīngcháng zhǎo bù dào dōngxi.

He is always forgetful and careless, often unable to find things.

这位同学常常丢三落四，需要提醒。

Zhè wèi tóngxué chángcháng diūsān làsì, xūyào tíxǐng.

This student often forgets things and is careless, needs reminders.

她丢三落四的习惯让她的家人很头疼。

Tā diūsān làsì de xíguàn ràng tā de jiārén hěn tóuténg.

Her habit of being forgetful and careless gives her family a headache.