How to Solve Proportions Using Cross Multiplication Solving Proportions Math with Mr J

welcome to math with mr in this video i'm going to cover how to solve proportion using cross multiplication now when solving proportions using cross multiplication we cross multiply set the cross products equal to each other and solve let's jump into number 1 where we have 3 to 12 equals 5 2x so is our unknown we need to find out what equals let's start by cross multiplying this just means to multiply diagonally this is going to give us an equation that we can solve for first we'll do times that gives us 3 we can bring our equal sign straight down and then we have times 5. now i'm going to use dot to represent multiplication that way there isn't any confusion between x's that are variables and then x's that are multiplication signs now we can do 12 times 5. so let's bring our 3x down equals well 12 times 5 that equals 60. so we have 3x equals 60. now we have one-step equation that we can solve to figure out what equals so we need to isolate that variable of we do that by dividing both sides by 3 so 3x divided by 3 and 60 divided by 3. 3x divided by 3 gives us and then 60 divided by 3 gives us 20. equals 20. now one more thing do want to mention about using cross multiplication to solve proportions don't get too held up on what numbers to multiply first or which diagonal you should put on which side of the equal sign it will all work out the same either way just make sure to multiply diagonally and have the equal sign in between your cross products let's move on to number two where we have 33 to equals six to two we'll start by cross multiplying so multiplying diagonally first we'll do 33 times two so we have 33 times two bring our equal sign down and then we have times 6 which we can write as next we can do 33 times 2 that gives us 66 bring our equal sign and 6x down now we have one-step equation that we can solve in order to figure out what equals we need to isolate that variable of and we can do that by dividing both sides by 6. 6x divided by 6 we'll isolate that and then we also need to do 66 divided by 6. 6x divided by 6 again isolates that variable so equals and then 66 divided by 6 gives us 11. so equals 11 and we can rewrite that as equals 11. so there you have it there's how you solve proportion using cross multiplication cross multiply set the cross products equal to each other and solve hope that helped thanks so much for watching until next time peace