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**Buying Puppy Food**

Every day, my mom pays me two dollars for doing chores around the house. I use this money to buy dog food for Sam. Each portion costs $1.25, and Sam eats two portions a day, which means I need $2.50 per day. I’ve been saving all my money for the past week. Will I have enough to buy food for Sam? Let’s write a software program to find out how much money I need to care for Sam.

- Cost per portion of puppy food: $1.25
- Portions needed per month: 60

### Let’s Write a Python Program

We’ll write a Python program to calculate the total monthly cost of puppy food.* Hint! Always press ENTER when you finish a line*.

>>> one_portion = 1.25

>>> portions_needed = 60

>>> total_cost = one_portion * portions_needed

>>> print(total_cost)

If you wrote the code correctly, the output should be: `$75`

**Explanation**

**Variable Creation:**

First, we create two variables,`one_portion`

and`portions_needed`

, and assign them the respective values.**Multiplication Calculation:**

We use the multiplication operator (`*`

) to calculate the total cost by multiplying the cost of one portion by the number of portions needed.*To type the multiplication symbol (operator), press*`Shift + 8`

**Displaying the Result:**

Finally, we print the total cost using`print(total_cost)`

**Can I afford to keep the puppy?**

Since my allowance is only $60 per month and dog food costs $75, I want to do more chores, but mom doesn’t have any additional ones available. Instead, she suggested that buying puppy food in bulk (a big box) might be cheaper. I saw a big poster at the store advertising a box containing 60 portions for $59.99, tax included.

- Big box cost: $59.99
- Portions in one big box: 60

Based on this bulk price, I can afford to feed Sam every month. But how much will it cost to feed Sam for an entire year? Let’s write a Python program to find out.

>>> box_cost = 59.99

>>> months = 12

>>> cost_per_year = box_cost * months

>>> print(cost_per_year)

By entering this code, you should get the total cost of dog food per year, which is $719.88. It’s quite a bit, but I can afford it because mom pays me for doing little jobs around the house.

**One More Challenge**

Every year, my aunt gives me $50 for my birthday. I plan to use that money to buy a leash so I can start taking Sam for walks every day. When I told Auntie that the leash I like costs $32, she asked me how much money I would have left over after buying it. Good question. Let’s write a Python program to find out.

>>> birthday_present = 50.00

>>> leash_cost = 32.00

>>> left_over_money = birthday_present – leash_cost

>>> print(left_over_money)

Python is an amazing language for solving all kinds of math problems. For basic calculations, you can use:

**Addition:**Use the`+`

operator`number_one + number_two`

**Subtraction:**Use the`-`

operator`number_one - number_two`

**Multiplication:**Use the`*`

operator`number_one * number_two`

*To type the multiplication operator, hold the Shift key and press 8.*

**Division:**Use the`/`

operator`number_one / number_two`

Now take a moment to reflect on the many calculations you can perform with these operators. Knowing how to add, subtract, multiply, and divide gives you numerous ways to solve mathematical problems.

**Quiz Time!**

Which key combination do we need to press in order to obtain the multiplication operator?

- Shift + x
- Ctl + 8
- Shift + m
- None of the above

Final Note:

Please don’t rush through this session. Learning a new programming language takes time and practice. Feel free to review today’s material, and when you feel ready, continue to the next session.