To convert the airplane's speed from kilometers per hour (km/h) to miles per hour (mph), you can use the conversion ratio:
1 km ≈ 0.62 miles.
Given that the airplane travels about 900 km/h, the calculation for miles per hour would be:
\[ 900 , \text{km/h} \times 0.62 , \text{miles/km} \]
Calculating this:
\[ 900 \times 0.62 = 558 , \text{mph} \]
Therefore, the airplane's speed in miles per hour is approximately 558 mph.
The correct answer is c) 558.