Paying exact money

Help Jincy pay the exact amount from her piggy bank.

In your book, Maths Mela (Chapter 4, We the Travellers — II), Jincy opens her piggy bank. She finds 8 coins of ₹1, 9 coins of ₹2 and 5 coins of ₹5. She wants to buy stickers worth ₹38 and pay the exact amount. Which coins can she use?

First, how much does she have? 8 coins of ₹1 make ₹8, 9 coins of ₹2 make ₹18, and 5 coins of ₹5 make ₹25. In all, ₹8 + ₹18 + ₹25 = ₹51. That is more than ₹38, so she can pay.

A good way is to start with the biggest coins. All 5 coins of ₹5 make ₹25. She still needs ₹38 − ₹25 = ₹13. 6 coins of ₹2 make ₹12, and 1 coin of ₹1 brings it to ₹13. So she can pay with 5 coins of ₹5, 6 coins of ₹2 and 1 coin of ₹1: ₹25 + ₹12 + ₹1 = ₹38.

There is more than one right answer! 4 coins of ₹5 (₹20) and all 9 coins of ₹2 (₹18) also make ₹38. Whatever coins she picks, check that they add up to exactly ₹38 and that she has that many of each coin.

To pay an exact amount, start with the biggest coins, find how much is still needed, and fill it with smaller coins, checking that the total is exact and that you have enough of each coin.

Practise this lesson

Questions that get harder as you improve, a Tutor that helps without giving the answer away, and progress you can see. Free for every learner.

Try it now Sign up free I have an account

No account, no email address. Opens the real product.