1. The problem asks for the smallest possible answer to the multiplication $20 \times 300$ given that Isaac estimated it by rounding each number to 1 significant figure. 2. Isaac's estimation is $20 \times 300 = 6000$ after rounding each number to 1 significant figure. 3. To find the smallest possible original multiplication, we need to consider the smallest numbers that round to 20 and 300 respectively when rounded to 1 significant figure. 4. For 20 rounded to 1 significant figure, the smallest number is $15$ because numbers from $15$ to $24.9$ round to $20$. 5. For 300 rounded to 1 significant figure, the smallest number is $250$ because numbers from $250$ to $349.9$ round to $300$. 6. Therefore, the smallest possible original multiplication is: $$ 15 \times 250 = 3750 $$ 7. This is the smallest product that would round to $6000$ when rounded to 1 significant figure for each factor. Final answer: $3750$