Math Story : Unitary Method
What Is The Cost?
Uncle Math : Kids! I have some bad news. We can’t go for the picnic as planned. I forgot to buy a few things for the strawberry cake. I won’t have time to go and buy them either because I have some urgent work in the lab.
Cirho : Oh no! I was really looking forward to the picnic.
Cirha : Yeah, me too. What should we do now?
Uncle Math : I’m really sorry, but we can’t go today.
Squarho : I wish we could buy those items ourselves, but we don’t know how much to pay the shopkeeper. It is always so confusing.
Uncle Math : Let me teach you how to calculate the prices when we buy things? We can still have the picnic and learn something new too.
Squarho, Cirha, Triho and Cirho : Hurray!
Uncle Math : You can use the unitary method for this. The unitary method helps us find the cost of one unit and then the cost of the required number of units. It simply follows the rule of “divide then multiply”. To determine the cost of the required number of units: first, calculate the cost of a single unit by dividing the total cost by the number of units specified, then multiply by the required number of units.
Squarho : I am not getting anything.
Uncle Math : No fear! When I am here. Let me explain with the help of an example. If a dozen mangoes cost 120 coins and you need to find the cost of 5 mangoes, first find the cost of one mango.
Cirho : I know this. We will divide 120 by 1, right?
Uncle Math : No dear! Since 1 dozen equals 12, to find the cost of 1 mango, divide 120 by 12.
Triho : That is 10. So, the cost of 1 mango is 10 coins, but how do we find the cost of 5 mangoes?
Uncle Math : Very simple! Now that you know the cost of 1 mango, which is 10 coins. Multiply 10 by 5 to get the cost of 5 mangoes.
Cirha : I got it, Uncle Math. 5 mangoes will cost 5 multiplied by 10, which is 50 coins. What do we need to buy for the cake?
Uncle Math : We need 3 litres of milk and 4 boxes of strawberries.
Cirha : Cirho and I will buy the required number of strawberry boxes.
Triho : Squarho and I will buy the required amount of milk.
Uncle Math : Okay, great. Meet me back here in an hour. Always remember to divide first, then multiply while shopping.
Narrator : An hour passed by, Squarho and Triho returned with the milk.
Uncle Math : Did you get the milk?
Triho : Yes, Uncle Math, we were a little confused at first, but we managed to figure it out.
Uncle Math : Okay, great. How much did it cost?
Triho : We followed your instructions exactly. We divided first, then multiplied. The milk costs 40 coins for 2 litres. We divided 40 by 2, which is 20. Am I right?
Uncle Math : That is right! And then?
Squarho : Since we needed 3 litres, we multiplied 3 by 20, which is 60. So, we paid 60 coins to the shopkeeper and got 3 litres of milk.
Uncle Math : That is fantastic! You both did a great job.
Triho and Squarho : Thank you, Uncle Math.
Narrator : Another hour passed, but Cirha and Cirho still did not return. They decided to look for them.
Triho : There they are. Are they crying?
Squarho : Oh no! I think so.
Uncle Math : Why are you both crying? What happened?
Cirho : Sorry, Uncle Math, we are confused about whether to divide first and then multiply, or multiply first and then divide.
Uncle Math : Okay, now stop crying. Tell me how much strawberry costs.
Cirha : The cost of 5 strawberry boxes is 250 coins, but we only need 4 boxes. We are totally confused.
Uncle Math : To find out the price of one box, we will first divide 250 by 5.
Cirha : This gives us 50. So, does it mean that the cost of 1 box of strawberries is 50 coins?
Uncle Math : Yes, You got it! Now, can you find the cost of 4 boxes?
Cirho : Now, we should multiply. So 50 multiplied by 4 is….ummm….. 200 coins.
Uncle Math : Well done! You both are correct. Let us quickly buy 4 boxes of strawberries and bake our cake for the picnic.
Narrator : Uncle Math bakes an amazing strawberry cake for them, and they all enjoy the picnic. It was a day filled with meaningful learning and an exciting picnic with yummy strawberry cake!
We Learnt That…
Let’s Discuss
Please refer this guide by Fun2Do Labs for teaching unitary method to kids :
