Discount, tax & compound interest
Sales, GST, percentage change and interest on interest.
Learn with Kutty
Go one screen at a time. Press Next when you are ready. Tap 🔊 Read to me to listen.
Compound interest is interest on interest: your money grows faster each year.
Look: ₹10,000 at 10% a year: +1,000, then +1,100, then +1,210.
✏️ Your turn!
Type your answer and press Check. Kutty will tell you if it is right.
1₹800 with 25% off?
2₹5,000 at 10% compound for 2 years?
3Price up 10% then down 10%: same as before?
! Careful!
✗Adding the same ₹1,000 every year.
✓That is simple interest. Compound uses the new total each year.
✗15% off then 18% on is just 3% more.
✓Each percent applies to a different amount. Do one step at a time.
See the whole lesson on one page
Compound interest is interest on interest: your money grows faster each year.
Each year the interest is added to the money. Next year’s interest is worked out on the new, bigger amount.
Think of it like thisA snowball rolling downhill picks up more snow the bigger it gets. Savings with compound interest grow the same way.
Solved together
₹10,000 is saved at 10% compound interest. How much after 3 years?
Year 1: add 10% of 10,000.
10,000 + 1,000 = 11,000Year 2: add 10% of 11,000.
11,000 + 1,100 = 12,100Year 3: add 10% of 12,100.
12,100 + 1,210 = 13,310
Answer₹13,310.
For older learners and grown-ups: a little more
Amount = P(1 + R/100)ⁿ. For ₹10,000 at 10% for 3 years: 10,000 × 1.1³ = 13,310.
Now practise it
Kanakku makes new questions on discount, tax & compound interest every time. It shows the working and gives a hint when you are stuck.