Question

On the first day in each month, Enid deposited $4 into her bank account and Jim deposited $3 into his. They opened these accounts on May 15, 1990. On December 31, 1990, they each had $72 dollars in their account. How much did each person deposit on May 15?

Answer 1

Answer:

The amount of money in Enid bank account can be written as a linear equation.

Ye = Xe + $4*m

where Ye is the money that Enid has in her account, m is the number of months that have passed since she opened it, and Xe is the initial deposit.

For Jim, the equation is similar:

Yj = Xj + $3*m

where Yj and Xj are similar as above.

Between May 15 and December 31 of the same year, we have 7 months (where i am counting December because the deposit is made in the first day of the month).

Then we have that:

Ye = $72 = Xe + $4*7 = Xe + $28

Xe = $72 - $28 = $44

So in May 15, Enid deposited $44.

For Jim we have:

Yj = $72 = Xj + $3*7 = Xj + $21

Xj = $72 - $21 = $51

So in May 15, Jim deposited $51.