Lesson 2
John has 4 more nickels than dimes in his pocket. Write an equation that represents, y, the value of the
money John has, in terms of x, the number of dimes John has.
Explain what the y-intercept of this equation represents.



Answer :

Sure, let's go through the process of creating the equation that represents the value of the money John has in terms of [tex]\( x \)[/tex], the number of dimes John has.

1. Identify the value of each type of coin:
- The value of one dime is [tex]$0.10. - The value of one nickel is $[/tex]0.05.

2. Express the number of nickels in terms of the number of dimes:
- According to the problem, John has 4 more nickels than dimes.
- If [tex]\( x \)[/tex] represents the number of dimes, then the number of nickels can be expressed as [tex]\( x + 4 \)[/tex].

3. Calculate the total value of the dimes:
- The value of [tex]\( x \)[/tex] dimes is [tex]\( 0.10x \)[/tex] dollars.

4. Calculate the total value of the nickels:
- The number of nickels is [tex]\( x + 4 \)[/tex].
- Thus, the value of the nickels is [tex]\( 0.05(x + 4) \)[/tex] dollars.

5. Combine the value of the dimes and nickels to get the total value:
- The total value, [tex]\( y \)[/tex], is the sum of the value of the dimes and the value of the nickels.
- Therefore, the equation is:
[tex]\[ y = 0.10x + 0.05(x + 4) \][/tex]

6. Simplify the equation if needed:
- Although simplification is optional here, it can make the equation look cleaner or easier to interpret.

Now, let's discuss the y-intercept of the equation.
The y-intercept is the value of [tex]\( y \)[/tex] when [tex]\( x = 0 \)[/tex].

1. Determine the y-intercept:
- Substitute [tex]\( x = 0 \)[/tex] into the equation [tex]\( y = 0.10x + 0.05(x + 4) \)[/tex]:
[tex]\[ y = 0.10(0) + 0.05(0 + 4) \][/tex]
- Simplify it:
[tex]\[ y = 0 + 0.05 \cdot 4 \][/tex]
- Calculate [tex]\( 0.05 \times 4 \)[/tex]:
[tex]\[ y = 0.20 \][/tex]

2. Interpret the y-intercept:
- The y-intercept, in this case, represents the total value of the nickels when the number of dimes ([tex]\( x \)[/tex]) is zero.
- So, if John has zero dimes, he still has the value of four nickels, which is $0.20.

In summary:

- The equation representing the total value of John's money in terms of [tex]\( x \)[/tex], the number of dimes, is:
[tex]\[ y = 0.10x + 0.05(x + 4) \][/tex]

- The y-intercept of this equation is 0.20, which represents the value of the nickels when John has no dimes.