s1=1a*1b=1ab
s2=1.3a*0.7b=0.91ab
Зменшилася,
(S1-S2/S1)*100%=(1ab-0.91ab/1ab)*100%=(0.09/1)*100%=9%
Зменшилася на 9%
s1=1a*1b=1ab
s2=1.3a*0.7b=0.91ab
Зменшилася,
(S1-S2/S1)*100%=(1ab-0.91ab/1ab)*100%=(0.09/1)*100%=9%
Зменшилася на 9%