the complete question in the attached figure
we know
the pool in the drawing is 15x7.5 and the scale is 3/1000
then
if the size in the drawing is 3----------------------> the actual is 1000
15------------------------------------< X
x=15*1000/3=5000 cms----- > 50 m
and
if the size in the drawing is 3----------------------> the actual is 1000
7.5------------------------------------< X
x=7.5*1000/3=2500 cm--------> 25 m
the actual area of the pool is 50*25=1250 m²
the answer is 1250 m²