iI just came across a fine line between the two words, and iI hope it works. itIt seems that in 'reducing',an an external force is used.
whenWhen we say
heHe has been _______ the intake of sugar since he was diagnosed with diabetes.
(reducing / decreasing) --> i vote forI would use "reduced" (somethingbecause it is something done by him).
while
theThe number of students, appearing for this paper, is __________ (.
(reducing / decreasing)--> i vote forI would use "decreasing" (somethingas it's something not done by anyone).