1.1. Dr. Ali is analysing the average heart rate of patients recorded by three doctors during a fitness study. Each doctor has a different number of patients, and Dr. Ali has recorded the mean heart rate for each doctor's patients.

The table below gives some information about the data.

Dr. Ali plans to use one of the following two methods to calculate the overall average heart rate for all patients across the three doctors.

Method 1
Calculate the mean of 72, 78, and 66.

Method 2
Given that Dr. Ali knows the value of $n$, calculate the weighted mean heart rate for the three doctors.

For each of these two methods, assess whether or not the method is an appropriate way to calculate the overall average heart rate of all the patients.

1.2. The weighted mean heart rate for the three doctors’ patients is 74.2 beats per minute, correct to one decimal place.

Calculate the value of $n$.