From the table, the conversion rate is constant, so divide feet by meters using any row:

So the actual conversion is about $3.28084$ feet per meter.

The student's estimate is $3.3$ feet per meter. Percent error is

Compute the difference:

Then

Rounded to the nearest tenth of a percent, this is $0.6\%$.

Therefore, the correct answer is $0.6\%$.

Let the amount of additive in the 300-milliliter solution be $0.18(300)=54$ milliliters. Let the amount of additive in the 500-milliliter solution be $\frac{x}{100}(500)=5x$ milliliters. Before dilution, the 800-milliliter mixture contains $54+5x$ milliliters of additive. Then 200 milliliters of pure water are added, so the total volume becomes 1,000 milliliters, but the amount of additive stays the same. Since the final concentration is $16\%$, the final amount of additive must be $0.16(1000)=160$ milliliters. So

Solving gives

and

Therefore, $x>20$ must be true.

The area of the original garden is $30\times 20=600$ square feet. The walkway's area is 60% of this, so the walkway has area $0.60(600)=360$ square feet.

Let the width of the walkway be $x$ feet. Since the walkway goes around the entire outside, the outer dimensions are $(30+2x)$ by $(20+2x)$. The total outer area is therefore $(30+2x)(20+2x)$.

Because the walkway alone has area 360,

So,

Expand:

Divide by 4:

Factor:

So $x=-30$ or $x=3$. A width cannot be negative, so $x=3$.

The width of the walkway is 3 feet.

The final solution must be 25% chemical, and the total volume is 7.2 liters. So the amount of chemical needed is $0.25(7.2)=1.8$ liters. Each bottle is labeled 500 milliliters, but each actually contains 4% less, so each bottle has $500(0.96)=480$ milliliters of chemical. Converting to liters, each bottle contains $0.48$ liter. Now divide the required chemical amount by the amount per bottle: $\frac{1.8}{0.48}=3.75$. Since 3.75 bottles are needed, the technician must open 4 whole bottles. Therefore, the least number of bottles is 4.

Let the original value be $x$. After an increase of $p\%$, the value becomes $x\left(1+\frac{p}{100}\right)$. Then decreasing that result by $20\%$ multiplies it by $0.8$, so the final value is

We are told this final value is $12\%$ greater than the original, so it also equals $1.12x$. Set the expressions equal:

Since $x\ne 0$, divide both sides by $x$:

Now divide by $0.8$:

Subtract 1:

Multiply by 100:

Therefore, the correct answer is $40$.