Karl needs a total of $30 to buy a bike. He has $12. He can earn $6 an hour babysitting. Which equation can be used to find the number of hours, $h$, Karl has to babysit to have the money he needs?
A. $30-6h+12=0$
B. $6+12h=30$
C. $6+h=12$
D. $6h+12=30
Answer (1)
Define the variable: Let h be the number of hours Karl needs to babysit.
Express Karl's earnings: Karl earns 6 h from babysitting.
Formulate the equation: The total money Karl has is 12 + 6 h , which must equal $30.
State the final equation: The equation to find the number of hours is 6 h + 12 = 30 .
Explanation
Problem Analysis Let's analyze the problem. Karl needs $30 to buy a bike and he already has $12. He earns $6 per hour babysitting. We need to find the equation that represents this situation, where 'h' is the number of hours he needs to babysit.
Earnings from Babysitting The money Karl earns from babysitting is $6 multiplied by the number of hours he works, which is 6 h .
Total Money To find the total amount of money Karl has, we add the money he already has ($12) to the money he earns babysitting ($6h). So, the total money is 12 + 6 h .
Setting up the Equation We know that Karl needs a total of $30 to buy the bike. Therefore, we set up the equation: 12 + 6 h = 30 . This equation states that the money he already has plus the money he earns babysitting must equal $30.
Final Equation The equation that represents the situation is 6 h + 12 = 30 .
Examples
Imagine you're saving up for a new video game that costs $60. You already have $20, and you earn $8 each week by doing chores. The equation 8h + 20 = 60 helps you calculate how many weeks (h) you need to do chores to save enough money for the game. This kind of problem is useful for budgeting and planning your savings goals.
