A gardener needs AT LEAST 10 units of chemical A. A jar gives 5 units and a carton 1 unit. The constraint is:

1. The phrase 'at least' sets a floor, not a ceiling, so the inequality points the greater-than way. 2. Each jar supplies 5 units of chemical A, so $x$ jars supply $5x$. 3. Each carton supplies 1 unit, so $y$ cartons supply $y$. 4. The total must reach the requirement: $5x+y\ge 10$. 5. Writing $\le$ instead of $\ge$ was the single most common recorded error, and it would let the gardener buy nothing at all. _Source: NECTA ACSEE 2022 Advanced Mathematics 142/1, Question 3: Linear Programming_