Video: Addition and Subtraction of Numbers up to 999 in a Real-World Context

The weekly income of a family is 781 pounds. The family spends 242 pounds on rent, 270 pounds on food, 129 on bills, and the rest is saved. How much does the family save?

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Video Transcript

The weekly income of a family is 781 pounds. The family spends 242 pounds on rent, 270 pounds on food, 129 on bills, and the rest is saved. How much does the family save?

We know the family’s weekly income is 781 pounds. And they spend 242 on rent, 270 on food, and 129 on bills. And the family saves the rest of the money. Before we can work out how much money they save, we need to work out how much money they spend. 242 on rent, 270 on food, and another 129 is spent on bills. We need to add together the total amount the family spends each week.

We can add these three numbers using column addition. Let’s start by adding in the ones column. We have two, zero, and nine. What is two plus zero plus nine? 11. We need to exchange the one. In the tens column, we’ve exchanged one. And we have to add four, seven, and two. Four plus seven is 11. Two more makes 13 plus the one we exchanged gives us a total of 14. We can write the four and exchange the one. Finally, we need to add in the hundreds column. Two plus two is four. One more makes five plus the one we exchanged gives us a total of six. So all together, the family spends 641 pounds each week.

To find out how much money the family has left over for their savings, we need to subtract the amount they spent from the amount they have, to begin with. Their income is 781. And they spend 641. So we need to subtract 641 from 781. In the ones, we have one. And we need to take away one, which leaves us with nothing. We have eight tens. And we need to take away four tens, which leaves us with four. And in the hundreds, we have seven hundreds. And we need to take away six, which leaves us with one. 781 take away 641 leaves us with 140 pounds. Each week, the family is able to save 140 pounds.

To find the answer, first we added together the total amount that the family spends each week. And we subtracted this from their income, which leaves the family with 140 pounds each week for saving.

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