Answer: The real tree house door should be 126 cm tall.
Explanation:
Given: Two students make a model of a tree house they want to build. The scale is 1:42.
i.e. 1 cm of model = 42 cm in real
if the in the scale model,the door is 3 cm tall, then the height of real tree house door = 3 x (42) cm
⇒ Height of real tree house door= 126 cm
Hence, the real tree house door should be 126 cm tall.
