The formula I = P × R × T
Explore why i=Interest (what you earn/pay), P=Principal (starting amount), R=Rate (as a decimal percentage), T=Time (in years).
In this lesson
The formula I = P × R × T is part of Simple Interest Math. This preview shows how interest-growth connects to everyday family decisions such as earning, saving, spending choices, goals, approvals, or parent-guided money conversations inside Progress Penguin.
Today’s money mission
Imagine this situation: Using I = P × R × T: Principal 15000 in local currency, Rate 8% per year, Time 3 years.
What you need to know
I=Interest (what you earn/pay), P=Principal (starting amount), R=Rate (as a decimal percentage), T=Time (in years). These four variables describe every simple interest calculation.
Real-life example
Real-life money moment: You want to earn 5000 in local currency interest. You have 25000 in local currency to save and can find a 10% annual rate.
Progress Penguin connection
Open your savings balance right now. Apply the formula I = P × R × T using your actual balance as P, your savings account rate as R, and 3 months as T. Calculate the interest you should earn in 3 months. Check back in 3 months and compare.
Activity preview
Try the money challenge
Match each key term from this lesson to its definition. The trickiest pair connects to: i=Interest (what you earn/pay), P=Principal (starting amount), R=Rate (as a decimal. If a match feels wrong, reread the guided explanation and try again.
Practice adding money to savings
Open Requests and make a deposit request into savings so you can see how saving starts. Parent approval can happen later.
Quiz preview
The simple interest formula is:
Using I = P × R × T: Principal 15000 in local currency, Rate 8% per year, Time 3 years. What is the interest?