Question

Suppose you have $30 to spend on bags of tootsie rolls that are worth $3 and bags of lollipops worth $5. If you have to use all of their money, what combinations of candy bags can they buy?

Construct a linear equation and find/explain the y-intercept, x-intercept, and slope.
Finally, if you have $45 to spend on the candy, how would that impact everything?

Answer 1

see below

Explanation:

Let x = tootsie rolls

y = lollipops

Toosie rolls are 3 dollars and lollipops are $5 and you only have 30 dollars.

3x+5y =30

To find the x intercept, set y=0 and solve for x

3x +0 = 30

3x = 30

Divide by 3

3x/3 = 30/3

x = 10

The x intercept is 10. This means if you get no lollipops, you can have ten tootsie rolls.

To find the y intercept, set x=0 and solve for y

0 +5y = 30

5y = 30

Divide by 5

5y/5 = 30/5

x = 6

The y intercept is 6. This means if you get no tootsie rolls you can have 6 lollipops.

To find the slope, solve the equation for y

3x+5y =30

Subtract 3x from each side

3x-3x+5y = -3x+30

5y = -3x+30

Divide by 5

y = -3/5 x +30/5

y = -3/5 x +6

The slope is -3/5. For every three less lollipops you get, you can have 5 more tootsie rolls.

If you have $45 dollars instead of 30, this will change the x and y intercepts, but not the slope.

3x+5y =45

To find the x intercept, set y=0 and solve for x

3x +0 = 45

3x = 45

Divide by 3

3x/3 = 45/3

x = 15

The x intercept is 15. This means if you get no lollipops, you can have 15 tootsie rolls.

To find the y intercept, set x=0 and solve for y

0 +5y = 45

5y = 45

Divide by 5

5y/5 = 45/5

x = 9

The y intercept is 9. This means if you get no tootsie rolls you can have 9 lollipops.

To find the slope, solve the equation for y

3x+5y =45

Subtract 3x from each side

3x-3x+5y = -3x+45

5y = -3x+45

Divide by 5

y = -3/5 x +45/5

y = -3/5 x +9

The slope is -3/5. For every three less lollipops you get, you can have 5 more tootsie rolls.