Question

Kee’s catering charges $100 to cater a party for 15 people and $12 for each additional person. What is the constant rate of change and the formula? (y = mx or y=mx+b)

Answer 1

The cost for a party here is the base fee, plus charges for any additional guests.

So we know for a 15-person party, the price is going to be $100. That's a flat (constant) cost.

We know that for each additional person, we add $12. So for $x$ more people, the cost is $$12x$.

Since 100 is constant here, we make that our y-intercept. Even with no additional guests, the cost is still $100.

We add to write $y=12x+100$. 12 is the constant rate of change (slope).