A sum of money when invested for a definite period at r% simple interest will yield an interest of rm80 .using the same interest rate, find the interest earned if the sum is tripled and the investment period is doubled

To begin, let's break down the given information:

Principal amount (P) = unknown
Interest rate (r) = unknown
Interest earned (I) = RM80

With simple interest formula: I = (P * r * t) / 100
We have the following equation: 80 = (P * r * t) / 100

Now, we need to find the interest earned when the sum is tripled and the investment period is doubled. So, let's use the same interest rate (r) and calculate the new interest earned.

New Principal amount (P') = 3P (as the sum is tripled)
New Investment period (t') = 2t (as the investment period is doubled)

The new interest formula becomes: I' = (P' * r * t') / 100

Substituting the values:
I' = (3P * r * 2t) / 100
I' = (6Prt) / 100

Therefore, the interest earned when the sum is tripled and the investment period is doubled is 6 times the original interest earned.

To calculate the new interest amount (I'), we can use the original interest earned (I = RM80) and find I' as follows:

I' = 6 * I
I' = 6 * 80
I' = RM480

Hence, the interest earned when the sum is tripled and the investment period is doubled is RM480.