Math Problem Statement

The system of equations D + N = 95 and 0.10D + 0.05N = 7.75 can be used to determine the number of dimes (D) and nickels (N) in a child's piggy bank. The goal is to estimate the number of each type of coin using a graph.

Solution

The system of equations provided is:

D+N=95D + N = 95 0.10D+0.05N=7.750.10D + 0.05N = 7.75

Where DD represents the number of dimes and NN represents the number of nickels.

Step 1: Solving the system algebraically

To solve for DD and NN, let's first eliminate one of the variables. We'll use substitution or elimination. For this explanation, let's use substitution.

  1. From the first equation: D+N=95    N=95DD + N = 95 \implies N = 95 - D

  2. Substitute N=95DN = 95 - D into the second equation: 0.10D+0.05(95D)=7.750.10D + 0.05(95 - D) = 7.75 Simplify: 0.10D+0.05(95)0.05D=7.750.10D + 0.05(95) - 0.05D = 7.75 0.10D+4.750.05D=7.750.10D + 4.75 - 0.05D = 7.75 Combine like terms: 0.05D+4.75=7.750.05D + 4.75 = 7.75 Subtract 4.75 from both sides: 0.05D=30.05D = 3 Solve for DD: D=30.05=60D = \frac{3}{0.05} = 60

  3. Now that D=60D = 60, substitute this into N=95DN = 95 - D: N=9560=35N = 95 - 60 = 35

Thus, the solution is D=60D = 60 dimes and N=35N = 35 nickels.

Graph interpretation:

The graph shows the intersection of the two lines at the point (60,35)(60, 35), which aligns with our solution.

Conclusion:

The correct answer is:

  • There are about 60 dimes and 35 nickels.

Would you like more details on this solution or how to interpret the graph further?

Here are some additional questions to explore:

  1. How would the solution change if the total number of coins was different?
  2. What happens if we change the value of one of the coin types (e.g., change nickel to 10 cents)?
  3. How could this system of equations be solved using matrices?
  4. What if the total amount of money was different (e.g., $10 instead of $7.75)?
  5. How can graphing systems of equations help in real-life problem-solving?

Tip: When solving systems of equations, substitution works well when one equation is easy to manipulate for a single variable.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Algebra
Systems of Linear Equations
Graphing

Formulas

D + N = 95
0.10D + 0.05N = 7.75

Theorems

Substitution Method
Graphical Interpretation of Systems of Equations

Suitable Grade Level

Grades 6-8