Answer: Approximately 23.0 cm
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Work Shown:
a = 20.3
b = unknown
c = 30.7
Apply the pythagorean theorem to find b
a^2 + b^2 = c^2
(20.3)^2 + b^2 = (30.7)^2
412.09 + b^2 = 942.49
b^2 = 942.49-412.09
b^2 = 530.4
b = sqrt(530.4)
b = 23.0304146727757 value is approximate
b = 23.0
I rounded to one decimal place because the other values (20.3 and 30.7) were to one decimal place.