## anonymous one year ago Avery has a total of $12.50 in her piggy bank at home. Each week she takes out$1.25 to ride the city bus. Write an equation representing the balance, C, in the piggy bank, where w is the number of weeks.

1. ganeshie8

Since the starting amount is $$12.50$$, the amount in her piggy bank in $$\text{week 0}$$ is $$12.50$$

2. ganeshie8

Can you guess the amount in her piggy bank during $$\text{week 1}$$ ?

3. anonymous

11.25

4. ganeshie8

Yes! because she takes out $$1.25$$ : $\large 12.50-\color{red}{1.25} = 11.25$

5. ganeshie8

can you guess the amount in her piggy band during $$\text{week 2}$$ ?

6. anonymous

10

7. ganeshie8

Correct! you must have worked it by subtracting $$1.25$$ again : $\large 12.50-\color{red}{1.25} -\color{red}{1.25} = 10$

8. anonymous

i know how to subtract. i just need help with how i write the equation. I know that it begins like "C=......"

9. ganeshie8

Notice the pattern ? can you find the amount in her piggy bank during $$\text{week} 8$$ ?

10. ganeshie8

you just need to subtract $$\color{red}{1.25}$$ for $$8$$ times right

11. ganeshie8

so the amount in the bank after $$w$$ weeks is given by : $C ~~=~~12.50~-~\color{red}{1.25}w$

12. anonymous

Those are my choices C = 1.25w – 12.50 C = 1.25w + 12.50 C = –1.25w + 12.50 C = –1.25w – 12.50

13. anonymous

Would i just move it around????

14. anonymous

I thought that it was C=12.50-1.25w but thats not up there.

15. ganeshie8

Yes $C ~~=~~12.50~-~\color{red}{1.25}w$ is same as $C ~~=~-~\color{red}{1.25}w~+~12.50$

16. anonymous

ohhhhhhh okay. haha. thats all i really needed to know. Thank you.

17. ganeshie8

yw!