Video: Comparing an Integer to the Result of Adding Three Decimals in Word Problems

Noah has $10 to buy candy. Can he buy a lollipop for $2.36, gummy bears for $4.38 a pack, and a bar of chocolate for $4.97?

04:12

Video Transcript

Noah has 10 dollars to buy candy. Can he buy a lollipop for two dollars 36, gummy bears for four dollars 38 a pack, and a bar of chocolate for 4 dollars 97?

There are only two possible answers to this question, either Noah can buy the candy or he can’t. It all depends on whether the total amount is more or less than 10 dollars. So we need to find the total of these three decimal amounts and then compare them to the whole number, 10 dollars. We can use column addition to add our decimals together. To begin with, we can set them out vertically. The lollipop costs two dollars 36. So we can write that as 2.36. Gummy bears cost four dollars 38 which we could write as 4.38. And then we also need to add the cost of a bar of chocolate for four dollars 97. Now, we could add all three numbers at the same time and write them all vertically; just do one addition.

But instead, let’s break the problem down into two additions. First, we’ll add the lollipop and the gummy bears together. And then to whatever the total is of that, we’ll add our four dollars 97 for the bar of chocolate. And this will give us our final total, which we can compare to the 10 dollars that Noah has to buy candy with. Now, something important before we start, let’s put decimal points in both of the places where we’re going to write our answers so that we know that our answers are going to have the correct place value. First, we can add the hundredths column. Six plus eight equals 14. 14 hundredths are the same as four hundredths and 10 tenths.

Now, we had our tenths. Three plus three equals six tenths. And we’ve got one tenth underneath that seven tenths in total. And finally, our whole dollars, two plus four equals six. So we can see that the cost of the lollipop and the gummy bears is six dollars 74. Now, before we add the cost of the bar of chocolate as well, we can make a prediction here. If we look at the whole dollars, in other words, the ones column, we can see that we’re adding six and four together. And we know that six and four makes 10. So the answer is going to be more than 10 dollars. We can predict that Noah is not going to be able to buy the lollipop, the gummy bears, and the bar of chocolate.

Let’s have the chocolate bar then onto our total, just to check that our prediction is correct. First, the hundredths, four plus seven equals 11 hundredths, which is the same as one tenth and one hundredth. Now, we add the tenth digits. Seven tenths plus nine tenths equals 16 tenths plus the one we’ve exchanged equals 17 tenths. That’s the same as seven tenths and one whole dollar or one one. Now, we can see although we thought our total might be 10 because we’ve exchanged one one as well, the total of our ones now is 11.

The cost of the lollipop, the gummy bears, and the bar of chocolate is 11 dollars 71. Noah has 10 dollars to buy candy. Can he buy a lollipop for two dollars 36, gummy bears for four dollars 38 a pack, and a bar of chocolate for four dollars 97? We found the answer by adding the three decimals together and comparing them to 10 dollars. The answer is no. Noah can’t buy these three types of sweet. The cost of them is more than 10 dollars.

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