A man invested a sum of ₦280.00 partly at 5% and partly at 4%, if the total interest is ₦12.80 per annum, find the amount invested at 5%.
Answer Details
Let x be the amount invested at 5% and y be the amount invested at 4%. Then we have the following system of equations:
x + y = 280 --- (1) (since the man invested a total of ₦280.00)
0.05x + 0.04y = 12.80 --- (2) (since the total interest earned is ₦12.80)
To solve for x, we can use the first equation to get y = 280 - x, and substitute into the second equation to get:
0.05x + 0.04(280 - x) = 12.80
Simplifying and solving for x, we get:
0.05x + 11.20 - 0.04x = 12.80
0.01x = 1.60
x = 160
Therefore, the amount invested at 5% is ₦160.00.