1 - Step Equations - Video 3 of 4
Math
Math Step Equations
Is J over 25 equals 24. Now this is not. The same as J over 25 times 24. These are different. And this is where a lot of students get confused. If there is an equal sign, I can take this equal sign and I look at this equals sign as a road. Underneath this 24, there's an imaginary one. There's always an imaginary one. What this road, I can cross the road. Cross the road. Which means to cross multiply. I can cross multiply. Over here, in this example, I can not. Cross multiply. And I know it's crazy because this is a multiplication symbol, but I can not cross multiply. When you have two fractions with the multiplication symbol, you actually have to multiply straight. Across.
You can not cross multiply. And I just heard someone mention that yesterday. Oh, I can just cross multiply. No, you can't. You can only cross multiply when there's an equal sign in the middle. So here we have J times one equals and then you can cross the road or cross multiply the other way. 25 times 24. And remember in order to do 25 times 24, all we did was a little bit. All we did was break the two on the four up. So we put that's 24. That's 25 times 20. And 25 times four. When we bring your zero straight down, two times 5 is ten. So you put a zero carry plus one. Now we have two times two plus one. Two times two is four plus one is 5.
Here you have four times 5, which is 20. You put a zero, carrier plus two. And now we multiply this way. So we have four times two, which is 8 plus two. It just ten. The last step is to add these two numbers together. Which is 600. So J is equal to 600. Over on this side, with the multiplication. Then multiplying straight across, we would have 24 times J so a letter and a number side by side means there's an imaginary little multiplication symbol in between. Over 25 times one is 25. So this would be the answer here. 24 J over 25, if we were multiplying. The next example.