What is the sum of the missing digits in the subtraction problem below? _ 4 _ 8 9 - 1 1 1 --------- 1 1 1 1 1 A. 8 B. 10 C. 11 D. Cannot be determined.

GATE 2017 · General Aptitude · Numerical Computation · medium

Answer: Cannot be determined — the missing digits are not uniquely fixed by the given constraints.

1. Convert subtraction to addition: So the full number should be 11222. But the known digits show _4_89. Position mismatch: 11222 does not end in 89.
2. Check column by column with borrow: Complex borrow chains make the problem under-constrained. Two different sets of missing digits can satisfy the constraints.