How to calculate ammeter and voltmeter readings?

Hint: As we know, an ammeter is an instrument that can measure the current in a circuit.
And, a voltmeter is an instrument that can measure the voltage in a circuit.
We have to remember that by applying Ohm’s law, the ammeter is connected in series with a circuit to measure the current passing through the circuit. And the voltmeter is connected in parallel to measure the potential difference of the two points of that circuit.

Complete step-by-step solution:
We also need to remember that an ammeter is an instrument that is connected in series with a circuit to measure the current passing through the circuit. From Ohm’s law, we get that $V = IR$ where, $V = $ voltage
$I = $ the current of the circuit.
And, $R = $ resistance
From this formula, the current is measured by regulating voltage with constant resistance.
A voltmeter is an instrument that can measure the voltage in a circuit i.e the potential difference between two points of a circuit. The voltmeter is connected in parallel series with the circuit.

Additional information: We have to remember that the galvanometer has functioned as a voltmeter when it is connected in series with a large resistance \[R\]. \[R\] is calculated by the maximum voltage measured.

Note: We need to know that the ammeter in the Series connection is necessary to measure current because it experiences the same current.
We must have to remember that the voltmeter in a parallel connection is necessary to measure voltage because it experiences the same potential difference.