Simple interest in one line

Principal times rate times time, all over a hundred.

The question

Find the simple interest on ₹8,000 at 5% for 3 years.

The trick

Simple interest = P × R × T ÷ 100. Cancel before you multiply and the numbers stay small.

Worked example

1P = 8000, R = 5, T = 3
2Cancel first: 8000 ÷ 100 = 80
380 × 5 × 3 = 1200
4Simple interest = ₹1,200

So: ₹1,200

Remember it like this

PRT over a hundred — say it as 'party over a hundred' and it sticks.

In the exam

Cancel the 100 against the principal before multiplying — you avoid a five-digit multiplication entirely. And watch the units: if the time is in months, divide by 12 before you start.

Why it works

The rate is a percentage per year. Dividing by 100 converts it to a decimal fraction, and multiplying by the number of years repeats that one-year interest.

Explain this to my childGet the words to teach it, in your language

Try it yourself

0/3 correct

1
SI on ₹5,000 at 4% for 2 years (number only)
SI on ₹5,000 at 4% for 2 years (number only)
2
SI on ₹12,000 at 10% for 1.5 years (number only)
SI on ₹12,000 at 10% for 1.5 years (number only)
3
SI on ₹2,500 at 8% for 4 years (number only)
SI on ₹2,500 at 8% for 4 years (number only)