State exam math question on Order of Operations (#10). 5th Grade Math

NGSS Science Videos

This video helps children prepare for state math exams by explaining how to solve a retired (released) question from an actual state exam.    - If you want to copy any of our more than 100 free Google Forms (all with questions and links to free-access educational videos we've made), then please download this free file from TPT and it will give you directions for how to access them: https://www.teacherspayteachers.com/Product/State-Math-Test-questions-and-answers-as-a-Google-Form-2022-Q6-10-V2-11530867   Other free resources we've made:  - For links to many free educational resources, please visit our website (no 3rd party advertising, no subscriptions, no paywalls): https://TestPrepLLC.org/   - For our free apps for Apple's Mac and iPad (collects no data, no advertising, no subscriptions, no paywalls, no in-app purchases), please visit our page on the Apple App Store. These apps include Common Core and State based practice tests in math, and State science exams based on NGSS and State curriculums (all with detailed, colorful explanations): https://apps.apple.com/us/developer/test-prep-llc/id1727786893   Best wishes,  The staff at Test Prep LLC  https://TestPrepLLC.org

Transcript

00:00This video is part of a Google Form quiz that teachers can assign to their students for homework.

00:06After the students submit their answers, then they can play a video like this one to see the

00:10answer explained. We've made more than 100 quizzes as Google Forms with free access videos,

00:17which teachers are welcome to copy for free. To get access to these, please see the link in the

00:22description. This video is based on a question from an actual state exam. You may have one like

00:28this on your state exam. If you've already done so, we suggest that you watch the video on

00:34Order of Operations and Substitution in Math before watching this video.

00:40Several expressions are shown. Which expressions have a value of 12 when r equals 3? Select the

00:47expressions you want to choose. To solve this problem, we need to calculate the value of each

00:53expression to see if it's equal to 12. In order to do that, we need to know about substitution

00:59and about the order of operations. Let's start with this expression, which is 21 minus 3 times r.

01:07First, we replace the multiplication x with an asterisk.

01:12Then, we do the substitution. We'll replace the letter r with the number 3.

01:16Next, we need to know which order to do the operations in. Here's a reminder of the order

01:23of operations. For elementary school, they're free boxes. The order of operations tells us which order

01:29to do things in. We start with the top box, then do the middle box, then do the bottom box.

01:36The order is parentheses, then multiply and divide, then add and subtract. One way to remember what words

01:43go in each box is to use a memory aid like this sentence. Please make drinks and sandwiches.

01:49The first letter of each word in the memory aid is the same as the first letter in the order of

01:54operations. We also write in a reminder that if both are present, then do the left ones before the

02:00right ones. There are no parentheses, so we'll move down to the red box. There's a multiplication

02:06operation here. 3 times 3 equals 9. We'll bring down the 21 and the minus sign. There's only one

02:13operation left, which is subtraction. 21 minus 9 equals 12. This expression's value is 12 when r equals 3.

02:22So this is a correct answer choice. Now, let's evaluate this answer option,

02:28which is 2 times r plus 4. First, we replace the multiplication x with an asterisk.

02:37Then, we do the substitution. We'll replace the letter r with the number 3.

02:44Next, we'll solve this by using the order of operations. There are no parentheses, so we'll move

02:49down to the red box. There's a multiplication operation here. 2 times 3 equals 6. We'll bring

02:56down the 4 and the plus sign. There's only one operation left, which is addition. 6 plus 4 equals 10.

03:04This expression's value is 10 when r equals 3, so this is not a correct answer choice.

03:10Now, let's evaluate this answer option, which is 5 times r minus 6. First, we replace the

03:17multiplication x with an asterisk. Then, we do the substitution. We'll replace the letter r with the

03:26number 3. Next, we'll solve this by using the order of operations. There are no parentheses,

03:35so we'll move down to the red box. There's a multiplication operation here.

03:405 times 3 equals 15. We'll bring down the 6 and the minus sign. There's only one operation left,

03:47which is subtraction. 15 minus 6 equals 9. This expression's value is 9 when r equals 3,

03:54so this is not a correct answer choice. Now, let's evaluate this answer option,

04:00which is 3 times r plus 3. First, we replace the multiplication x with an asterisk.

04:09Then, we do the substitution. We'll replace the letter r with the number 3.

04:17Next, we'll solve this by using the order of operations. There are no parentheses,

04:22so we'll move down to the red box. There's a multiplication operation here. 3 times 3 equals 9.

04:29We'll bring down the 3 in the plus sign. There's only one operation left, which is addition.

04:359 plus 3 equals 12. This expression's value is 12 when r equals 3, so this is a correct answer choice.

04:44Now, let's evaluate this answer option, which is 2 times r plus 6. First, we replace the

04:50multiplication x with an asterisk. Then, we do the substitution. We'll replace the letter r with the

04:59number 3. Next, we'll solve this by using the order of operations. There are no parentheses,

05:08so we'll move down to the red box. There's a multiplication operation here. 2 times 3 equals

05:146. We'll bring down the 6 and the plus sign. There's only one operation left, which is addition.

05:216 plus 6 equals 12. This expression's value is 12 when r equals 3, so this is a correct answer choice.

05:30Now, let's evaluate this answer option, which is 14 minus 4 times r. First, we replace the

05:37multiplication x with an asterisk. Then, we do the substitution. We'll replace the letter r with the

05:45number 3. Next, we'll solve this by using the order of operations. There are no parentheses,

05:54so we'll move down to the red box. There's a multiplication operation here. 4 times 3 equals

06:0012. We'll bring down the 14 and the minus sign. There's only one operation left, which is subtraction.

06:0814 minus 12 equals 2. This expression's value is 2 when r equals 3, so this is not a correct answer choice.

06:1615 minus 6. This expression is a good example.

06:3015 minus sign.

06:3415 minus sign.

06:3616 minus sign.

06:3716 minus sign.

06:4316 minus sign.

06:4416 degrees.

06:4416 minus sign.

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