Compare the masculine and feminine forms side by side.
FeminineMasculineNumber
فَاعِلَةٌفَاعِلٌSingular
فَاعِلَتَانِفَاعِلَانِDual
فَاعِلَاتٌفَاعِلُوْنَPlural
The feminine forms are easy to spot because their endings differ clearly from the masculine set.