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.