1.1. A student investigated how the total resistance of a circuit varied with resistors placed in parallel.

Figure 1 shows the circuit the student used.

Figure 1

The resistance of each resistor is identical.

The student used an ohmmeter to measure the total resistance.

The student took multiple readings and calculated a mean.

Table 1 shows their results.

Table 1

Determine the missing value X for Reading 3.

1.2. Explain how calculating a mean increases the accuracy of the data.

1.3. The student took a fourth reading.

Reading 4 = 15.2 Ω

The student's partner said that Reading 4 should not be included in the mean.

Justify whether you agree with the student's partner.

1.4. The student plotted a graph of the data they produced in their investigation. Figure 2 shows the graph. 

Figure 2

Use the graph in Figure 2 to identify the relationship between the mean total resistance and the number of resistors in parallel.