3.2.10 write first step questions

Number two is multiply or divide and then number three is add or subtract. And I'm going to show you why this is so important to do the operations in order. Because if you don't, you can get the wrong answer. If you haven't finished writing this down, this is a great time to pause because I'm going to go on. All right, so I've got this equation. Ten minus three equals two. Now, I have it written two times because I'm going to do it two different ways. First, I'm just going to do it from left to right, just like we usually do our math equation. So I have ten takeaway three, which is 7. And then I'm going to times by two, which is equal to 14. Over here, I'm going to follow my order of operations. So I'm going to leave that ten alone for right now. And I'm going to do this chunk. Three times two. And three times two is 6. 

Now I'm going to do ten takeaway 6, which is four. Look at how radically different my answers are. So to make sure everyone has the same answer to problems like this one, people have decided that multiplication and division will be done before addition and subtraction. The answer we found in green over here is the correct answer. That's why I made it green, red means like stop. That's wrong. But I like to use red a lot anyways. That's just a side note. If you want to tell people to add or subtract first, then that's when you must use parentheses to tell them that you want them to add or subtract first, because parentheses sees mean, do this first. For example, if you want people to subtract first in here, then you would put parentheses around the ten and the three. 

If you wanted people to do the problem this way. Okay? So quick review, order of operations, parentheses, do this first. Multiply or divide, and the number three add or subtract. So let's try some word problems. Now, these are all going to be two step word problems. I'm going to scroll down here just so you can see this for a second. Tips for two step problems. Think what is the first step question? Now today and on our homework, we're going to actually be writing the first step question just to get us used to thinking about it. And then remember, don't stop in the middle of the problem. Once you've done that first step, you haven't found your answer. A good thing once you're done with your answer to do is reread the question to make sure you're done with that problem. So let's take a look at our first two step problem. A roller coaster has 7 cars. Each car has four seats. 

If there were empty seats, how many people were on the roller coaster? How many people were on the roller coaster? Well, there's three empty seats. Oh, I don't think I'm ready for that part yet. I need to find how many seats there are in all. Oh, so my first step question is how many seats are on the roller coaster? Then I need to figure out that first step part. So if I have 7 cars on the roller coaster, each car has four seats, that's equal groups, so I have to do 7 times four equals 28. So I know that there's 28 seats on the roller coaster. I'm not done with my problem. Remember, don't stop in the middle of the problem. Keep going. If there were three empty seats, well, I know that there's 28 seats and three of them are empty. I'm going to subtract those three off the 28. And 28 takeaway three is equal to 25. So I know I have 25 people riding on that roller coaster. 

So if I were to write this whole problem into one. Equation, I did 7 times four, and then I took away three equaling 25. So I did 7 times four that's multiplication first, and then I subtracted the three equaling 25. I personally think that it's easier just to do two problems. 7 times four is 28, and then taking that 28 and taking away the three. That's how I like to do things. You might be different than me. All right, Marta earns $10 babysitting. She always spends $3 and saves the rest. How much money does she save in 8 weeks? I ought to think about my question. My first step question, I know that this is a two step problem. What's the first step? Marta earns $10 babysitting, and she always spends $3 of it. So she doesn't have all the ten left. So my question would be, how much does Marta save each week? So that would be ten, oops. Hold on. 

On this problem I'll show you how to write the whole equation and then solve it. So my first part of the equation is ten takeaway three. That's the first thing I need to do. And then it says, how much does she save in 8 weeks? Well, she'd saves ten takeaway three, every 8 weeks, so that's multiple times. But I don't want to do the multiplication first. My first step was to figure out ten takeaway three. That's where parentheses come in. So ten takeaway three would be 7, 7 times 8 is equal to 56. Whoops, that's not a 6. So she saves $56 in 8 weeks. Here's how I would do that problem. Ten, take away three is equal to 7. And then I would move down or over or somewhere else and do 7 times 8 is equal to 56. I would do it in two separate equations, but you can do it if you understand how to do it in one equation. That's fine. I'm showing you that either way works. 

All right, our last story problem for today, and then I'm going to give you a couple to work on for your homework. Abu about 6 packs of stickers. Each pack had 8 stickers, then a booze friend gave him ten more stickers. How many stickers does a boo have now? Remember, our first step in a two step problem is to figure out what that first question would be. So Abu baht 6 packs of stickers. Each pack had 8 stickers. While I'm wonder how many stickers Abu bat. That would be my question. How many stickers did a boo buy? That brings us up to here in our question. So that one, if I can make another text box here, move it up. That part of the problem is 6 times 8. Now we have to keep going because that's not our complete problem. Then a booze friend gave him ten more stickers. Then he added ten more stickers. How many stickers does a boo have now? So I could put an S for stickers. So this is how the situation equation would look from our problem up here our word problem. 

I don't need to add any parentheses because I have multiplication coming first and then addition. Now for me, I think that it's easier to do 6 times 8 is equal to. Is 46, right? 8 times 5 is 40 and then 6 more or 8 times 48. A times 5 is 40, I broke the 6 down and then one more group of 8 is 48. All right, 6 times 8 is 48. And then I would take that 48 and add ten. Oops, that was an addition sign. Which is equal to 58. So S. Is equal to 58 stickers. Remember your label. Okay? So in these next two problems that I'm going to give you on your paper, I want you to write the first step problem and then solve it. You can either solve it as one equation, or you can break it up into your two steps. Break it up into your two equations, whichever way makes sense to you, whichever way is easiest for you. We know that math can be done a lot of different ways. And these are the two ways that this kind of problem can be done. So you get to choose on what makes sense for you.

Here are your two problems for tonight. Remember to write me that first step question. Then solve the problem. On both of these, both of these are two step problems write me what the first step question is going to be and then solve the problem. Once you're done with these two problems, you are done for the night. So nice job. If you need to hit pause, this is a great time to do that. I'll leave it running for a couple seconds so that annoying red plaything, if you need to see a word, you can push play and it won't go right off. Okay? So have a great night tonight. Nice job. We'll see you tomorrow.