Question

1. Two of your friends, Matt and Karen, both run to you to settle a dispute. They were working on a math problem, and got different answers. Wisely, you decide to look at their work to see if you can spot the source of confusion.

Matt

6 – 4(3 – 5)2 + 30 ÷ 5
6 – 4(–2)2 + 30 ÷ 5
6 – 4(4) + 30 ÷ 5
6 – 16 + 30 ÷ 5
−10 + 30 ÷ 5
20 ÷ 5
4

Karen
6 – 4(3 – 5)2 + 30 ÷ 5
6 – 4(–2)2 + 30 ÷ 5
6 – 4(−4) + 30 ÷ 5
6 + 16 + 30 ÷ 5
6 + 16 + 6
22 + 6
28

My teacher said they are both wrong, so i need to know where they went wrong.

Answer 1

@protected

Answer 2

Is that \[(3-5)^2\]?

Answer 3

no it is 6 - 4*(3-5)*2 +30 / 5

Answer 4

Karen is right. Tell your teacher, she is a wee bit mistaken.

Answer 5

You have to use the PEMDAS or BODMAS here.

Answer 6

Matt is wrong in two steps.

-4(-4) \(\neq\) -16

\(−10 + 30 ÷ 5 \neq 20 ÷ 5\)

Answer 7

thank you :)

Answer 8

−10 + 30 ÷ 5
20 ÷ 5

wrong here

Answer 9

Matt is incorrect:

−10 + 30 ÷ 5 20 ÷ 5

Answer 10

This was answered recently.
http://openstudy.com/users/mathstudent55#/updates/5403ba72e4b0e197b3e3a26c

Answer 11

@AkashdeepDeb
Karen is also incorrect.

6 – 4(–2)^2 + 30 ÷ 5
6 – 4(−4) + 30 ÷ 5 should be 6 – 4(4) + 30 ÷ 5
since (-2)^2 = 4, not -4

Answer 12

@mathstuden55 are you talking to me?

Answer 13

I was answering @AkashdeepDeb who said the poster's teacher was wrong because only Matt is incorrect whereas the teacher said both Matt and Karen are wrong. The teacher is correct. The poster wrote (3 - 5)2 to mean (3 - 5)^2, so this is 4, not -4.

Answer 14

Oh yeah, lol! Excuse me, I'm not the best at math. I'll go in English!

Answer 15

Click on the link to see where this problem has already been dealt with.
There you see clearly (and in color) where the errors are in both Matt's and Karen's answers.

Answer 16

What link?

Answer 17

@Pollylovesschool Your answer is correct, but you only pointed out Matt's error. Karen also has an error.

Answer 18

This link:
http://openstudy.com/users/mathstudent55#/updates/5403ba72e4b0e197b3e3a26c

Answer 19

6 – 4(–2)^2 + 30 ÷ 5 6 – 4(−4) + 30 ÷ 5 should be 6 – 4(4) + 30 ÷ 5

Yeah Karen is incorrect too, I wasn't really thinking hard.

Answer 20

Thanks guys :)

Answer 21

You're welcome.

Answer 22

@mathstudent55
I said the teacher was wrong because the question was framed incorrectly. No exponents are shown.

Answer 23

@AkashdeepDeb
If you have been working on OS for any amount of time, you should already have noticed that posters very often write expressions such as x2 and (x + 3)3 when they mean \(x^2\) and \((x + 3)^3\), respectively. The teacher was not wrong. At worst, the poster did not post the question correctly, but the poster did post in a way that is very common, and most people on OS helping with problems know how to interpret. Also, if you try WolframAlfa and input the equation x2 + 2x + 1 = 0, it will interpret it correctly as \(x^2 + 2x + 1 = 0\).

Answer 24

@mathstudent55

Answer 25

@mathstudent55 is correct at that point