Answer:
the length of the road that runs straight from the school to the mall is 65 km
Explanation:
Refer the attached figure
AB denotes the distance between park and school
i.e. AB = 39 km
BC denotes the distance between park and mall i.e. 52 km
So, to calculate the distance between MALL and SCHOOL ie. AC
Use Pythagoras theorem i.e.







Hence the length of the road that runs straight from the school to the mall is 65 km