#### Answer

a) $≈ 12in$
b) $≈ 50mph$
c) $≈ 3mile$
d) $≈ 0.25in$

#### Work Step by Step

Using data from the approximation table specified in the question, multiply each of the given units by the ratio between units.
a) $30cm \times \frac{4in}{10cm} ≈ 12ft$
b) $25m/s \times \frac{2mph}{1m/s} ≈ 50mph$
c) $5km \times \frac{0.6mile}{1km} ≈ 3miles$
d) $0.5cm \times \frac{0.5in}{1cm} ≈ 0.25in$