A mobile service has 800 subscribers. A promotion raises the count by 50%, then 20% of the updated subscribers leave. Enter the final subscriber count.

Explication

The count changes by multipliers of 1.50 and 0.80, so 800 × 1.50 × 0.80 = 960. Subtracting the rates to claim a 30% rise would give 1040 and ignores the updated base.