The average weightof 12 articles is 18 kg. Addition of another new article reduces the average weight by 500g. What is the weight of the new article?

1 kg = 1000 gm

18 kg =18000gms

given that average weight of 12 articles is 18000gm

$$\frac{sum\ of\ total\ weight}{12}$$=18000

sum of total weight =216000

given that addition of new article reduces the average weight by 500gm

i.e,$$\frac{\left(sum\ of\ total\ weight+weight\ of\ new\ article\right)}{13}$$= 18000-500

$$\frac{\left(216000+weight\ of\ new\ article\right)}{13}=17500$$

216000+weight of new article=227500

weight of new article=11500

i.e;11.5kg

Hence answer is option A