Answer: 47.36 feet.
Step-by-step explanation:
When two quantities x and y are directly proportional , then the equation that shows direct variation is given by :-
[tex]\dfrac{x_1}{y_1}=\dfrac{x_2}{y_2}[/tex]
Given : The shadow cast by an object on a sunny day is directly proportional to the height of the object.
Let x be the height of tree.
According to the the given question , we have
[tex]\dfrac{x}{34}=\dfrac{78}{56}\\\\\Rightarrow\ x=\dfrac{78\times34}{56}\\\\\Rightarrow\ x=47.3571428571\approx47.36[/tex]
Hence, the height of tree = 47.36 feet.