Question Video: Converting Masses from Kilograms to Grams Mathematics

Video Transcript

Noah bought two and one-quarter kilograms of carrots and four and one-quarter kilograms of apples. How many grams of food did he buy?

Let’s begin this question by writing the value of the kilograms of carrots and apples in a more mathematical way. We’re told that the mass of carrots is two and one-quarter, which we can write as the whole number two and a fraction of one-quarter. The units of mass is the metric unit of kilograms. Noah also bought four and one-quarter kilograms of apples, so we can write that as four and one-quarter. We have the same units of kilograms. We’re asked to work out how many grams of food; that’s the total mass. We notice here that we’re asked in terms of grams rather than kilograms. We can approach this in two ways. We could either convert both of these masses in kilograms into grams and then add. Or we could add them first and then convert to grams.

Here, I’m going to add them first. In order to add two and a quarter and four and a quarter, we can add the whole numbers of two and four, giving us six. We can then add a quarter and a quarter, giving us two-quarters. But we can also simplify this fraction to one-half, so we know that the total mass is six and a half kilograms. We can recall that in one kilogram, there’s 1000 grams. When it comes to converting six and a half kilograms, it’s helpful to remember that the decimal form of this would be 6.5 kilograms. So we have 6.5, and we multiply it by 1000 to find the mass in grams, which is 6500 grams. And so we’ve answered the question that Noah bought 6500 grams of food.