Use ratio box to solve this problem. The patient doctor ratio at the large hospital was 20 to 1. If there were 48 doctors, how many patients were there?

We can set up a ratio box like this:

| | Doctors | Patients |
|--------------|-------|------------|
| Ratio | 20:1 | ? |
| Actual Amount | 48 | ? |

To solve for the missing amount of patients, we can use cross multiplication. First, we can simplify the ratio 20:1 to just 20. Then, we can set up the equation:

20 (doctors) = 1 (patient)
48 (doctors) = x (patients)

Cross multiplying, we get:

20 * x = 1 * 48

Simplifying:

x = 48/20

x = 2.4

Since we can't have a fractional amount of patients, we round up to the nearest whole number. Therefore, the answer is:

There were 3 patients for every 1 doctor, so if there were 48 doctors, there were 48 x 3 = 144 patients.