Answer: he invested $9000 in Fund B
Explanation:
Let x represent the amount which he invested in the account returning 6% profit.
Let y represent the amount which he invested in the account returning 2% profit.
The amount he invested in fund A was 3 times as much as the amount he invested in Fund B.. This means that
x = 3y
The formula for determining simple interest is expressed as
I = PRT/100
Considering the account returning 6% profit,
P = $x
T = 1 year
R = 6℅
I = (x × 6 × 1)/100 = 0.06x
Considering the account paying 2% interest,
P = $y
T = 1 year
R = 2℅
I = (y × 2 × 1)/100 = 0.02y
if the total profit from the two funds together was $1800, it means that
0.06x + 0.02y = 1800 - - - - - - - - - -1
Substituting x = 3y into equation 1, it becomes
0.06 × 3y + 0.02y = 1800
0.18y + 0.02y = 1800
0.2y = 1800
y = 1800/0.2 = 9000
x = 3y = 3 × 9000
x = 27000