Interest rates explained
Explore why a percentage rate applies to the principal.
In this lesson
Interest rates explained is part of What Is Interest?. 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: A savings account offers 7% annual interest. You deposit 20000 in local currency.
What you need to know
A percentage rate applies to the principal. 5%=5 per 100. On 1,000 that is 50. On 100,000 that is 5,000. The rate scales with the amount.
Real-life example
Real-life money moment: Which saves more over 2 years: 50000 in local currency at 10% or 80000 in local currency at 5%? (Simple interest) — 50,000×10%×2=10,000. 80,000×5%×2=8,000. The higher rate wins here despite the smaller principal. But note: at some principal size the larger amount would win. Rate×principal determines the outcome.
Progress Penguin connection
Open your savings account interest rate (check with a parent if needed) and calculate: what would ₦10,000 earn in one year at that rate? In two years? How many years before the interest earned equals ₦1,000? Each answer makes the rate concrete.
Activity preview
Try the money challenge
Match each key term from this lesson to its definition. The trickiest pair connects to: a percentage rate applies to the principal. 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
An interest rate of 8% on 1000 in local currency for one year is:
A savings account offers 7% annual interest. You deposit 20000 in local currency. How much interest do you earn in 1 year?