Walt made an extra $7000 last year from a part-time job. He invested part of the money at 10% and the rest at 7%. He made a total of $580 in interest. How much was invested at 7%?Select one:
We know that Interest= PNR/ 100. where P is the principal R is the rate of Interest N is the no of years the sum has been invested for. Since N is not given we assume that to be 1 Therefore we have 10x /100 + (7000 -x)*7/100= 580
Multiplying both sides by 100 10x+(7000-x)*7 = 58000 simplifying 10x+ 49000 - 7x = 58000 3x = 58000-49000 3x = 9000 x= 3000 therefore the sum of money invested at 7% = 7000 - 3000 = 4000
