A father invests certain amount of money at 6%. His son also invests one-third the amount his father invested, at 7%. If their combined income in one year is $250, how much did the son invest?
a. $1000
b. $2000
c. $3000
d. $4000

Question

gw2011 · Answer

The answer is (a) $1000.  Here is how I got the answer:

Let x= father's investment

0.06x+(0.07)(1/3)(x)=250
0.06x+(0.07/3)(x)=250  Multiply by 3 to eliminate the denominator
0.18x+0.07x=750
0.25x=750
x=$3000  This is the father's investment

(1/3)(3000)=$1000  This is the son's investment