Question

Jada had some dimes and quarters that had a total value of $12.50. The relationship between the number of dimes, d, and the number of quarters, q, can be expressed by the equation

01.d + 0.25q = 12.5.
1. If Jada has 4 quarters, how many dimes does she have?
2. If Jada has 10 quarters, how many dimes does she have?
3. Is the number of dimes a function of the number of quarters? If yes, write a rule (that starts with d =...) that you can use to determine the output, d, from a given input, q. If no, explain why not.

Answer 1

1. 115. If q=4, then the equation tells us that 0.1d+(0.25)⋅4=12.5. Subtracting 1 from both sides gives 0.1d=11.5, so d=115.

2. 100. If q=10, then the equation tells us that 0.1d+(0.25)⋅10=12.5. Subtracting 2.5 from both sides gives 0.1d=10, so d=100.

3. Yes. If you know the number of quarters, then you can determine the number of dimes from the equation. We can even write the equation in a way that shows this: d=125−2.5q. The expression 125−2.5qrepresents the output—it is the rule that determines the output d from a given input q.

Answer 2

Hi! This might be long but I hope it helps!

1. 115. If q=4, then the equation tells us that 0.1d+(0.25)⋅4=12.5. Subtracting 1 from both sides gives 0.1d=11.5, so d=115.

2. 100. If q=10, then the equation tells us that 0.1d+(0.25)⋅10=12.5. Subtracting 2.5 from both sides gives 0.1d=10, so d=100.

3. Yes. If you know the number of quarters, then you can determine the number of dimes from the equation. We can even write the equation in a way that shows this: d=125−2.5q. The expression 125−2.5qrepresents the output—it is the rule that determines the output d from a given input q.