a sum required to earn a monthly income of 1200 at 18% per annum then SI?

Since the period of time is not mentioned, it will be assumed that it is a perpetual annuity, with initial sum S generating interest of $1200 per month forever.

18% APR = 1.5% per month.
Therefore
S*0.015=1200, or
S=1200/0.015=80000

To calculate the sum required to earn a monthly income of 1200 at 18% per annum, we need to use the formula for Simple Interest (SI):

SI = (P * R * T) / 100

Where:
SI = Simple Interest
P = Principal (sum required)
R = Rate of Interest (in this case, 18% per annum)
T = Time (in this case, for a month)

First, let's convert the annual interest rate to a monthly rate. Since there are 12 months in a year, we divide the annual rate by 12:

Monthly Interest Rate = Annual Interest Rate / 12
= 18% / 12
= 1.5%

Next, we need to convert the monthly income of 1200 into an annual income:

Annual Income = Monthly Income * 12
= 1200 * 12
= 14400

Now, we can rearrange the formula to solve for the principal (sum required):

P = (SI * 100) / (R * T)
P = (14400 * 100) / (1.5 * 1)

Plugging in the values, we get:

P = 960,000

Therefore, the sum required to earn a monthly income of 1200 at 18% per annum is 960,000.

SI?

https://en.wikipedia.org/wiki/Si