The 5-digit number PQRST (all distinct digits) is such that T ≠ 0. P is thrice T. S is greater than Q by 4, while Q is greater than R by 3. How many such 5-digit numbers are possible ?

1. **Analyze Chain 1 (P, T):** The rule is $P = 3T$. Since $P$ must be a single digit ($0-9$) and $T \neq 0$: - If $T=1$, then $P=3$. Pair A: {1, 3} - If $T=2$, then $P=6$. Pair B: {2, 6} - If $T=3$, then $P=9$. Pair C: {3, 9} - ($T=4$ mak