To convert 1 4/5 inches to decimal measurements, add the whole number part to the fractional part. Therefore, Rob should order a case that is 1.8 inches wide.
To convert 1 4/5 inches to decimal measurements, we can add the whole number part (1) to the fractional part. The fractional part can be converted to decimal by dividing the numerator (4) by the denominator (5).
1 + 4/5 = 1 + 0.8 = 1.8 inches
Therefore, Rob should order a case that is 1.8 inches wide (option A).