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Social StudiesHumanitiesHigh schoolKey Stages 4 and 5

A supply and demand lesson where each student runs the numbers for their own game-day stand

One high schooler finds the price where her bubble tea stand sells out with nobody left waiting, works out what a $6 minimum price leaves over, and finds out from her own Revenue column that a higher price doesn't always bring in more money.

Jemel Fanfan

Jemel Fanfan | Founding Member at Flint

Title card reading 'A supply and demand lesson where each student runs the numbers for their own game-day stand', next to three cards from a student's chat: finding the $5 equilibrium in her spreadsheet, working out 50 left over at a $6 minimum price, and revenue falling from $550 to $480 after a 20% price rise while charger revenue rises from $200 to $216.

"Flint empowers my quicker students to design their own next steps, while others receive tailored AI support. They learn more effectively through AI role-plays, such as simulating CEO decisions, and by tackling exam questions with instant feedback."

Albert SchramAlbert Schram, Business and Economics Teacher at Nexus International School

Why this matters

A student can draw supply and demand curves and still believe that raising a price always brings in more money. She is half right: each sale earns more. She misses the buyers who walk away, so she misreads every elasticity question, and the teacher has to wait for quiz day to find out.

Camila prices bubble tea for a home game

Camila is a high schooler who wants to sell bubble tea at her school's home basketball games. She knows a lower price sells more cups. She thinks a higher price always means more money.

Every student gets the same greeting, the same market numbers and the same questions: the price where the stand sells out, what a $6 minimum price does, and what a 20% price rise does to revenue. The rest of the chat is Camila's own. Sparky names the spreadsheet and graph after what she said she'd sell, and each next message depends on what she just answered. Camila and her chat are an example we wrote for this page, shortened from a test run of the activity in which a student sent these same messages.

Sparky builds the market around the student's productSparky sends the student back to a row or a line instead of giving the answerA right answer gets a harder question
C

Camila

Interest: Selling bubble tea at home gamesStarting point: Knows a lower price sells moreGets stuck: Thinks a higher price always earns more

Sparky

Hi! Today you're the CEO of a stand at your school's home basketball game. You'll set a price, see how many people buy, and find out what happens when the student council steps in. First, what would you sell at the game?

Camila

bubble tea!! everyone at my school is obsessed with it

Sparky

Your Bubble Tea Stand – Home Game spreadsheet is ready. Number Wanted is how many customers want one at each price, and Number Made is how many your stand produces. Leftover (+) or Short (-) shows whether you have extras or run out, and Revenue is what you earn. At which price does the stand sell everything it makes, with nobody who wanted one left without it?
A spreadsheet Sparky made in the chat, titled Bubble Tea Stand – Home Game. Columns: Price, Number Wanted, Number Made, Leftover (+) or Short (-), Number Sold and Revenue. Rows for prices $2 to $8. At $5, 110 are wanted and 110 are made, the Leftover column is 0 and revenue is 550. At $6, 80 are wanted, 130 are made, 50 are left over and revenue is 480.
SpreadsheetBubble Tea Stand – Home Game

Camila

$2, because thats when the most people want one

Sparky

Check the Leftover (+) or Short (-) column on the $2 row. What does that number tell you about what's happening at the stand?

Camila

oh its -150, so 150 people want one and dont get it. so $5? thats the row where its 0

Sparky

Exactly. When that column hits 0, the number wanted equals the number made. That's called the equilibrium price: 110 bubble teas at $5. Now the student council has set a minimum price of $6 for anything sold at games. How many bubble teas will your stand have left over at the end of the game? And where does that show up on the graph?
A graph Sparky drew from the student's spreadsheet rows: price from $2 to $8 on the vertical axis and quantity on the horizontal axis. A blue demand line slopes down and a green supply line slopes up. They cross at 110 and $5, marked Equilibrium. A red dashed line at $6 is labeled Minimum price, and it crosses demand at 80 and supply at 130.
GraphBubble Tea Stand – Supply & Demand

Camila

50. at $6 i make 130 but only 80 people want one

Sparky

That's right, 50 left over. And where on the graph can you see those 50?

Camila

its the space between the demand line and the supply line on the dashed line

Sparky

Exactly. A minimum price set above equilibrium is called a price floor, and the leftovers are a surplus. The council drops the rule. If you raise the price from $5 to $6, a 20% increase, what happens to your revenue?

Camila

it goes up. higher price means more money per cup

Sparky

Take a look at the Revenue column on the $5 and $6 rows in your spreadsheet. What do those two numbers tell you?

Camila

wait it goes down, 550 to 480. i guess they just get a soda or a slushie from the snack bar instead

Understanding check

Yes. 30 fewer people buy, and that pulls revenue down even though each cup earns more. Your stand also sells the only phone chargers at the game. At $10 you sell 20, and at $12, also a 20% rise, you sell 18. What happens to charger revenue, and why is it different from bubble tea?

Camila

it goes up, 200 to 216. if your phone is dying theres nowhere else to get a charger so people pay anyway

Sparky

$200 to $216, and your reason is right. Bubble tea demand is elastic: buyers switch to other options when the price rises, so revenue falls. Charger demand is inelastic: buyers keep paying because there's nothing else at the game, so revenue rises. In one or two sentences, how should a CEO decide whether to raise a price?

Found equilibrium and the surplus herself, then fixed her idea that a higher price always earns more

Camila's first answer picked the price with the most buyers. Sparky didn't tell her she was wrong. It sent her to the $2 row of her own spreadsheet, where -150 showed her 150 people leaving without a drink, and she found $5 herself. When she said a higher price always earns more, Sparky pointed her to two numbers in her Revenue column, and she worked out why on her own: the people who stop buying get a soda instead. Sparky used the words equilibrium, price floor, surplus, elastic and inelastic only after she had described each idea in her own words.

What Flint did for Camila

  • Sparky made a spreadsheet for her bubble tea stand whose formulas recalculate, so every number she used came from a row she could check.
  • Sparky drew a supply and demand graph from her rows and added the $6 minimum price when the council's rule came in.
  • When Camila picked $2 and later said revenue goes up, Sparky sent her to a row and a column instead of giving the answer.
  • After each right answer, Sparky moved her to a harder question: the $6 floor, then the price rise, then the phone chargers.
  • Sparky worked out the charger revenue, $200 and $216, before it told Camila her numbers were right.

A teacher can't build 30 spreadsheets and graphs and watch each student read their own Revenue column. Sparky does it in every student's chat.

The activity page shows who thinks a higher price always earns more

Sparky's analysis guidelines in this activity ask it to note which students first said a higher price always brings in more revenue, and whether they changed their answer after reading the Revenue column. When a student stays stuck, Sparky adds an alert under Needs attention while the class is still working. When students submit, Sparky grades each chat against the activity's rubric: equilibrium, the price floor, and elasticity and revenue.

Flint's activity page for an activity called Run the Game-Day Stand: Supply, Demand and Price. Needs attention shows a live alert that one student has said three times that raising the price always brings in more money, after two hints about the Revenue column. Activity analytics lists what the class does well, including 23 students who found the 50 left over at the $6 minimum price, an area of improvement where 12 students first said a higher price always brings in more revenue, and a follow-up with a button to create a follow-up activity. The Sessions table shows two submitted students graded Proficient and Developing and one still in progress.

Example activity page

After an economics class finishes the game-day stand activity

The school and students are made up for this page. In this example, 12 students started out saying a higher price always earns more, so the follow-up has them sort products as elastic or inelastic by asking what else a buyer could get instead.

Set up the activity for free

The game-day stand activity is in Flint's public library, with Sparky's guidelines, the market numbers, the greeting and a rubric already set up. Open it, select Try this activity to copy it into a free Flint account, and move it to a class. In the activity settings, select Try session myself to price a stand as a student before you assign it.

For more social studies activities, see Flint for social studies.

Start the activity for free

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