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Zorluk: OrtaLinear Equations in One Variable

A customer opens a savings account with an initial deposit of $180\$180 and deposits $30\$30 at the end of each week. Two weeks later, a second customer opens a savings account with an initial deposit of $120\$120 and deposits $50\$50 at the end of each week. If neither customer makes any other deposits or withdrawals, after how many weeks from the time the first customer opened their account will both accounts have the same balance?

Cevap: 8 weeks

Cevap

Both accounts will have the same balance after 8 weeks.
The correct answer is 8. Letting ww represent the number of weeks since the first customer opened their account, the balance of the first account can be modeled by the expression 180+30w180 + 30w. Since the second customer opens their account two weeks later, the number of weeks they have been depositing money is w2w - 2. Therefore, the balance of the second account can be modeled by the expression 120+50(w2)120 + 50(w - 2). Setting the two expressions equal to find when the balances are the same gives the equation 180+30w=120+50(w2)180 + 30w = 120 + 50(w - 2). Distributing the 5050 yields 180+30w=120+50w100180 + 30w = 120 + 50w - 100. Simplifying the right side gives 180+30w=50w+20180 + 30w = 50w + 20. Subtracting 30w30w and 2020 from both sides of the equation yields 160=20w160 = 20w. Dividing both sides by 2020 gives w=8w = 8.

Adım Adım Çözüm

1
Set up expressions for the balance of each account after ww weeks.
First account balance: 180+30w180 + 30w; Second account balance: 120+50(w2)120 + 50(w - 2)
The first customer has been depositing for ww weeks. The second customer started 2 weeks later, so they have been depositing for w2w - 2 weeks.
2
Set the two expressions equal to each other to find when the balances are equal.
180+30w=120+50(w2)180 + 30w = 120 + 50(w - 2)
We want to find the number of weeks ww when the two account balances are equal.
3
Solve the linear equation for ww.
w=8w = 8
Distribute the 50 to get 180+30w=120+50w100180 + 30w = 120 + 50w - 100. Combine constants to get 180+30w=50w+20180 + 30w = 50w + 20. Subtract 30w30w and 2020 from both sides to get 160=20w160 = 20w. Divide by 2020 to get w=8w = 8.

Anahtar Kavram

Formulating and solving linear equations in one variable from real-world contexts
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