Answer: the additional amount to be invested is $5520
Explanation:
Let x represent the additional amount of money that should be added.
An investment of $4600 is made at an annual simple interest rate of 6.8%. It means that the amount of interest that would be made from this amount after 1 year is
6.8/100 × 4600 = $312.8
$x would be invested at 9%. It means that the amount of interest that would be made from this amount after 1 year is
9/100 × x = $0.09x
If the total interest to be earned is 8%, It means that the amount of interest that would be made from the total amount after 1 year is
0.08(x + 4600)
Therefore,
0.09x + 312.8 = 0.08(x + 4600)
0.09x + 312.8 = 0.08x + 368
0.09x - 0.08x = 368 - 312.8
0.01x = 55.2
x = 55.2/0.01
x = $5520