GMAT Problem Solving (PS) | There is a pentagon such that AB=BC=CD=DE, ∠B=∠ACD=∠ADE=90, and AE=20,

AB=BC=CD=DE

\(AE^2 = AD^2 + DE^2 = DE^2 + AC^2 + DC^2 = DE^2 + DC^2 + AB^2 + BC^2 = 4 AB^2\)

\(400 = 4 AB^2\)

\(AB^2 = 100\)
AB = 10

Hence option E is correct
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