To calculate the slope of the line passing through points M1(200, 30) and M2(40, 10), we can use the formula:

slope = (y2 - y1) / (x2 - x1)

where:
x1 = 200
y1 = 30
x2 = 40
y2 = 10

Substitute the values into the formula:

slope = (10 - 30) / (40 - 200)
slope = (-20) / (-160)
slope = 0.125

Therefore, the slope of the line passing through points M1 and M2 is 0.125.