## Prealgebra (7th Edition)

The diskette is: $90\text{ mm}$ wide.
If we want to convert from inch to centimeters, we have to consider the following conversion rate: $1\text{ in}=2.54\text{ cm}$ We multiply both sides by $3\frac{1}{2}$ in order to get the answer to the question: $3\frac{1}{2} \text{ in} =3\frac{1}{2}\times 2.54\text{ cm}=8.89\text{ cm}$ After that, we convert from centimeters to millimeters: $1 \text{ cm}=10\text{ mm}$ We multiply both sides by 8.89: $8.89 \text{ ft}= 88.9\text{ mm}$ By rounding it to the nearest ten we can say that the diskette is: $90\text{ mm}$ wide.