Answer:
0.5 cm per 10 degrees
0.05 cm per one degree.
Explanation:
For 30 degrees the bridge has a gap of 1.4 cm
For 40 degrees the bridge has a gap of 0.9 cm
The bridge expanded
1.4 cm - 0.9 cm = 0.5 cm per 10 degrees
Or, likewise
0.5/10 = 0.05 cm per one degree.
This means that for each degree that the temperature increases, the bridge will expand 0.05 cm