Question

9th grade math What is the function rule?How many weeks will it take for her to buy the bike? weeks. How much money will she have in 20 weeks?

Answer 1

1) The function rule is y = 15x + 50

2) 4 weeks

3) $350

1) Here, we start by writing the function rule

Let y be the total amount of money she would have saved in a particular week

Let x be the number of weeks

She has $50 already

So the equation will be;

$y\text{ = 15x + 50}$

2) From the question, we are told that the bike costs $100

So, to get the number of weeks, we simply substitute 100 for y

we have;

$\begin{gathered} 100\text{ = 15x + 50} \\ \\ 15x\text{ = 100-50} \\ \\ 15x\text{ = 50} \\ \\ x\text{ = }\frac{50}{15}\text{ = }\frac{10}{3}=\text{ 3}\frac{1}{3} \end{gathered}$

Now, the number of weeks cannot be fractional and the savings cannot be complete in 3 weeks

So we say it will take 4 weeks to buy the bike

3) To get this, we simply substitute x for 20

Thus, we have;

$\begin{gathered} y\text{ = 15(20) + 50} \\ \\ y\text{ = 300 + 50 = 350} \end{gathered}$