**Solution:**

HCF(420, 130) will give the maximum number of barfis that can be placed in each stack.

By Euclid’s division algorithm,

420 = 130 x 3 + 30

130 = 30 x 4 + 10

30 = 10 x 3 + 0

So, HCF(420, 130) = 10

Hence, the sweetseller can make stacks of 10 for both kinds of barfi.