If the length is 8.5, then 2 times the length is 17. Then the perimeter is 24, so 2 times the width is 24 minus 17 equals 7, and the width is half of 7 or 3.5. The area is then the product of the length and the width, or 8.5 times 3.5.
You should round to the nearest whole square unit, since the LEAST precise measure was the perimeter given to the nearest whole unit. You should never provide the result of a calculation involving measurements to a greater precision than the least precise of the given measurements.
John
My calculator said it, I believe it, that settles it
