A man invested a sum of N280.00 partly at 59% and partly at 4%. If the total interest is N12.80 per annum, find the amount invested at 5%.
.05x + .04(280-x) = 12.80
now just solve for x
To find the amount invested at 4%, let's assume the amount invested at 4% is x.
The amount invested at 59% can be calculated as follows:
N280.00 - x (amount invested at 4%) = amount invested at 59%
Now, let's calculate the interest earned from the amount invested at 4%:
x (amount invested at 4%) * 0.04 (4% converted to decimal) = interest earned
Next, let's calculate the interest earned from the amount invested at 59%:
(N280.00 - x) (amount invested at 59%) * 0.59 (59% converted to decimal) = interest earned
Since the total interest earned is N12.80 per annum, we can set up the equation:
0.04x + 0.59(N280.00 - x) = N12.80
Simplifying the equation:
0.04x + 165.2 - 0.59x = N12.80
-0.55x + 165.2 = N12.80
-0.55x = N12.80 - 165.2
-0.55x = -N152.40
Now, we can solve for x:
x = (-N152.40) / -0.55
x = N276.73 (approx.)
Therefore, the amount invested at 4% is approximately N276.73.