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**Find the intensity of Rainfall When the duration of Rainfall is Given**

First of all, we need to know the formula used to determine rainfall intensity. There are three types of empirical formula, they are

a) For storm duration 5 to 20 minutes

b) For storm duration 20 to 100 minutes

c) Where rainfall is frequent

Here, i = Intensity of rainfall in mm/hr, t = duration of storm in minutes.

Following are the two mathematical example for the determination of rainfall intensity

**Mathematical Problem: 1**

Find the intensity of rainfall when the storm continues for a period of 75 minutes.

**Solution:**

As the duration of rainfall is in between 20 to 100 minutes, so the formula will be

The intensity of rainfall,

**Mathematical Problem: 2**

Find the intensity of rainfall when the rainfall occurs frequently and the total duration of rainfall is 115 minutes:

**Solution:**

As the rainfall occurs frequently, we will use 3rd formula,

So, the intensity of rainfall is