The Interest Equation
See how Principal, Rate, and Time work together to grow your money.
Equation
y = (2000 * 5 * x) / 100
Graph
Table
| x | y |
|---|---|
| 1 | 100 |
| 2 | 200 |
| 3 | 300 |
| 4 | 400 |
| 5 | 500 |
| 6 | 600 |
| 7 | 700 |
| 8 | 800 |
| 9 | 900 |
| 10 | 1000 |
What this lesson covers
What you do
You shape the function y = (P * R * x) / 100 and watch the graph answer.
Challenges to clear
- Earn Rs 600 in 2 years at 6%: set P = 5000 and R = 6, then read the x = 2 row of the table.
- Time grows money: with the same P and R, after 5 years the interest is Rs 1500.
- A bigger loan: slide the principal P to 8000.
- Now find the rate that earns Rs 800 in 2 years. Interest per year is P × R ÷ 100 — so two years give twice that.
Check yourself
If you triple the Principal (P) but keep Rate (R) and Time (T) the same, what happens to the Simple Interest?
- The Interest triples. — correct
- The Interest doubles.
- The Interest stays the same because the Rate didn't change.
- The Interest becomes one-third.
Think about it
- If you double the Principal, what happens to the Interest?
- If the bank doubles the Rate, how does the Interest change?