investment question
posted by Joe .
scott and laura have both invested some money. Scott invested $3,000 more then laura and at a 2% higher interest rate. If scott received $800 annual interest and laura received $400, how much did scott invest?

Let their investments be L (Laura) and S (Scott). Laura's annual interest rate is I (expressed as a decimal) and Scott's is I + 0.02
S = L + 3000
800 = S*(I + 0.02)
400 = L I
You have three equations in three unknowns, which is enough to solve for all of them.
800 =(L+300)(I+0.02)
800 = LI + 300I +0.02L + 6
= 400 + 300I + 0.02L+ 6
= 400 + 300*400/L + 0.02L + 6
= 406 + 120000/L +0.02L
This can be turned into a quadratic equation for L. Take the positive root. 
Actually, you should take the negative root. You should plug both answers into the original equation to see which one fits. The one that makes sense (i.e. 800=800) should be the correct one.
Don't forget that Scott invested 3,000 more than Sally (S = L + 3000). You just solved for L. The question is asking for what S is. You're not done yet.
Respond to this Question
Similar Questions

math
Mrs. Brighton invested $30,000 and received a total of $2,300 in interest. If she invested part of the money at 10% and the remainder at 5%, then how much did she invest at each rate? 
math
Different Interest Rates. Mrs. Brighton invested $30,000 and received a total of $2300 in interest. If she invested part of the money at 10% and the remainder at 5%, then how much did she invest at each rate? 
Accounting
Scott Brothers, Inc. follows the qualitative characteristic of consistency. This means that Answer a. Scott applies the same accounting principles as its competitors. b. Scott has elected certain accounting principles that can never … 
college algebra
Scott and Laura have both invested some money. Scott invested $2500 more than Laura and at a 3% higher interest rate. If Scott received $900 annual interest and Laura received $450, how much did Scott invest? 
College alerbra
Scott invested a total of $9500 at two separate banks. One bank pays simple interest of 11% per year while the other pays simple interest at a rate of 9% per year. If Scott earned $973.00 in interest during a single year, how much … 
Please check Statistic
Is this correct four of the volunteer will receive the new medication, while the other four will receive a placebo as part of a double blind experiment. Starting at the left of the list of random numbers below and reading from left … 
math
Mr Joyce invested $ 25,000, part at 4% interest and the remainder at 7% interest. The total income he received from his investment was $1,450. How much did he invest at each interest rate? 
math
Mrs. Crawford has invested $ 6,000 at 3% interest. How much additional money should she invest at 8% interest so that the total income will be 4% of her total investment? 
Algebra
A woman invested some money at 8% and some at 9% annual simple interest. The interest for 1 year on the combined investment of $10,000 was $860. How much was invested at each rate? 
Algebra 2
Aimee inherited $15,000. She chose to invest it in a series of municipal bonds, mutual funds, and money market accounts, which paid annual interest rates of 5%, 6%, and 4%, respectively. She invested $2,000 more in mutual funds than …