Original Principle, different rates/investment

SaltyPoro

New member
Joined
Nov 6, 2017
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15
Linus and Macy put the same amount of money into different investments for one year. Linus' investments increased by 8%. Macy's investments decreased by 7%. The difference in the value of their investments was $750 after the one year. What was the original amount of money that each invested?
How do I start to solve this?
Do I just substitute the known values into I=PRT and solve for P, or is there a different equation that is meant to be used. :confused:
 

SaltyPoro

New member
Joined
Nov 6, 2017
Messages
15
Hint:
a = amount invested
a@8% - a@-7% = 750
a(1 + .08) - a(1 - .07) = 750
Solve for a
a(1 + 0.08) - a(1 -0.07) = 750
a(1.08) - a(0.93) = 750
1.08 - 0.93 = 0.15
0.15 * a = 0.15a
750/0.15 = a
a = 5000
This is correct right?
 
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