Bob has two savings accounts. He deposited $100 more into account B than account A. After a period of time, account A has earned $105 in interest at 7%, and account B has earned $80 in interest at a rate of 5%.
1. Write an equation to represent the situation. Explain each variable used.
2. How much money did Bob initially deposit into each account? Solve the equation.
I dont understand this..Please help!!

Question

Bob has two savings accounts. He deposited $100 more into account B than account A. After a period of time, account A has earned $105 in interest at 7%, and account B has earned $80 in interest at a rate of 5%. 
1. Write an equation to represent the situation. Explain each variable used.
2. How much money did Bob initially deposit into each account? Solve the equation.
I dont understand this..Please help!!

anonymous · Answer

Please help me! I need to know this before the test!

hero · Answer

B = A + 100
.07A + .05B = 185

anonymous · Answer

What do I do after that?

hero · Answer

Use substitution to substitute the expression for B into the second equation:

.07A + .05(A + 100) = 185

anonymous · Answer

Oh I think I see...Do I subsitute?

hero · Answer

After substitution, you solve for A, then for B

anonymous · Answer

0.12A=85?

hero · Answer

I think you rushed it.

hero · Answer

You forgot to distribute the .05

anonymous · Answer

Oh Ok, now How do I get the B part?

hero · Answer

@MattzSkatinn...one step at a time. Try solving for A first.

anonymous · Answer

I think A=1500

hero · Answer

Okay, so according to the original formulas, B will be $100 more, right?

anonymous · Answer

Soo..1600?

hero · Answer

Good job bro

hero · Answer

By the way, the first formula represents the amount of B in terms of A
The second formula represents total interest.

anonymous · Answer

Thanks so much! I think I understand it now!

anonymous · Answer

That I dont understand..

anonymous · Answer

So he deposited 1500 into A and 1600 into B? @Hero

hero · Answer

Yes

anonymous · Answer

Ok, and I dont understand what you meant by what the formulas represent

hero · Answer

A = amount invested in account A
B = amount invested in Account B

He deposited $100 more into account B than account A:
B = A + 100

Account A has earned $105 in interest at 7%, and account B has earned $80 in interest at a rate of 5%:
.07A + .05B = 185

hero · Answer

Maybe that will help you understand better. Each sentence can be translated into an equation.

hero · Answer

The first equation is obvious. The trick to the second equation is realizing that 105 + 80 gives you total interest. Once this is realized, you try to write an equation for total interest, or rather an equation that expresses 185 in terms of accounts A and B.

anonymous · Answer

Ok I think I understand..

hero · Answer

Can also be solved using

I = PRT if you're familiar with that