In the sum

$\otimes + 1 \otimes + 5 \otimes + \otimes \otimes + \otimes 1 = 1 \otimes \otimes$

for which digit does the symbol $\otimes$ stand?

Kepler. Discussing PYQs. Q.no. 11

In the sum ⊗+1⊗+5⊗+⊗⊗+⊗1=1⊗⊗\otimes + 1 \otimes + 5 \otimes + \otimes \otimes + \otimes 1 = 1 \otimes \otimes⊗+1⊗+5⊗+⊗⊗+⊗1=1⊗⊗ for which digit does the symbol ⊗\otimes⊗ stand?