Using the principle of common difference , we can observe that the distance moved per roll increases by a constant amount of centimeters . Hence, the distance moved in the 5th roll is 180 cm
Setting up a proportional relationship :
The common difference between each roll can be obtained thus :
d2 - d1 = d3 - d2 = d4 - d3
60 - 20 = 100 - 60 = 140 - 100
40 = 40 = 40
Hence, the common difference = 40
The distance obtained on the fifth roll :
d(5) = d(4) + common difference
d(5) = 140 + 40
d(5) = 180
Therefore, the distance obtained on the fifth roll is 180 cm
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