Laspeyres' Method prices the SAME base-year basket at both years' prices, using base-year quantities as the fixed weight. …

Step 1 — Compute $p_1q_0$ and $p_0q_0$ for each commodity.

Cross-check by re-multiplying each row independently. Recomputing $p_1q_0$ for each commodity in reverse order (D, C, B, A: 210, 300, 300, 300) and re-summing still gives 1110, and re-summing $p_0q_0$ in …

Using $q_1$ (current-year quantity) instead of $q_0$ in BOTH the numerator and denominator — Laspeyres' defining feature is that the SAME quantity basket ($q_0$) weights both years; mixing in $q_1$ …