In the given figure, A1, A2 and A3 are ideal ammeters. If

In the given figure, A₁, A₂ and A₃ are ideal ammeters. If A₁ reads 5A, A₂ reads 12 A, then A₃ should read

Since the source is an a.c voltage, therefore
I _3rms = √I_1rms ² + I_2rms ²
= √5² +12² = 13 A