Spark & Anvil Privacy

Teach & case

Help a near-peer reason through a money idea — when you explain it, you understand it best — then read the real decision it comes from.

A case · you decide

Priya's $50 question

Priya — a 16-year-old with a part-time job and her first $50 a month to spare

The idea in play: compound interest — interest earns interest, so it grows faster than it looks.

Priya just got her first steady paycheck — about $50 a month to spare. Her cousin says, "You're 16, there's no point saving yet — start when you actually earn real money." She isn't sure he's right.

She opens a compound-interest calculator. At a 7% average annual return, $50 a month feels tiny — barely one video game.

But the total at the bottom keeps climbing in a way that isn't just adding up her deposits. The interest starts earning its own interest — the part her cousin's advice quietly ignores.

Her cousin says waiting a few years won't matter much. Is that right?

She only has $50 now. Wait until she can invest "a real amount"?

Run your own numbers in the Decision Lab →

When two ideas meet: 2 cases with two people

A case · you decide

Priya and Odette: growth you can actually spend

Priya & Odette — a saver watching her balance compound, and a friend who asks what it will buy

The idea in play: compound growth and inflation compound against each other; what matters is the real return, growth divided by the rise in prices.

Priya puts $1,000 in an account paying 5% a year and leaves it for ten years. The balance will be about $1,629.

Odette points out that prices also rise. If inflation averages 3% a year, the same groceries cost about 34% more after ten years.

So the question is not how many dollars Priya will have. It is how much those dollars will buy.

In today's money, what is Priya's $1,629 worth after ten years of 3% inflation?

Open the Decision Lab →

A case · you decide

Cyrus and Rosa: the best return you can get

Cyrus & Rosa — a friend carrying a credit-card balance, and a saver deciding where a spare $500 should go

The idea in play: paying off debt earns exactly its interest rate, risk-free; so paying down high-interest debt usually beats saving at a lower rate.

Rosa has $500 spare. Cyrus has a $500 card balance at 22% a year. Rosa's savings account pays 4%.

Left alone for a year, the card balance grows by about $110. The savings account would earn about $20.

If the $500 were Cyrus's to use, where should it go?

Open the Decision Lab →