Final answer:
The interquartile range (IQR) is 40.
Step-by-step explanation:
The interquartile range (IQR) is a measure of the spread of the middle half, or the middle 50 percent, of the data. It is calculated by subtracting the first quartile (Q1) from the third quartile (Q3). In this case, the first quartile is 50 and the third quartile is 90, so the IQR is 90 - 50 = 40.