Calculation of Simple Interest:
The formula to calculate simple interest is:
Simple Interest = (Principal * Rate * Time) / 100

Given:
Principal = Rs. 5,000
Rate = 10% per annum
Time = 120 days (from 22nd March 2019 to 20th July 2019)

Conversion of Time:
To calculate the simple interest, the time needs to be converted into years. Since the given time is in days, we need to convert it into years by dividing it by 365.

Time = 120 days / 365 days/year = 0.3288 years

Calculation of Simple Interest:
Substituting the given values into the formula, we get:

Simple Interest = (5000 * 10 * 0.3288) / 100

Simplifying the equation, we have:

Simple Interest = 164.4

Therefore, the simple interest on Rs. 5,000 from 22nd March 2019 to 20th July 2019 at 10% interest per annum is Rs. 164.4.

Explanation:
To calculate the simple interest, we first need to convert the given time into years. This is important because the rate of interest is given per annum. In this case, the given time is 120 days, which is equivalent to 0.3288 years when divided by 365.

After converting the time, we can substitute the values into the formula for simple interest. The formula is derived from the concept that interest is calculated based on the principal amount, the rate of interest, and the time period.

In this case, the principal amount is Rs. 5,000, the rate of interest is 10% per annum, and the time period is 0.3288 years. By substituting these values into the formula, we can calculate the simple interest.

Simplifying the equation gives us the simple interest of Rs. 164.4. This means that for a principal amount of Rs. 5,000, the interest earned over the given time period is Rs. 164.4.

Final Answer:
Therefore, the simple interest on Rs. 5,000 from 22nd March 2019 to 20th July 2019 at 10% interest per annum is Rs. 164.4.