(a)According to the question, in the diagram given
Let us consider that RXY be the resistance between X and Y
Therefore, 1 / RXY = 1 / 10 + 1 / 40
1 / RXY = 5 / 40 ohm
This implies RXY = 8 ohm
Let us consider that the net resistance between points A and B be RAB
Thus, 1 / RAB = 10 ohm
Hence, the total resistance of the circuit = 18 ohm
(b) Current I = Voltage / Total resistance
I = 1.8 / 18 A
I = 0.1 A
thus, ammeter reading is 0.1 A