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Bob's Blunders

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Alla P.

on 13 January 2015

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Transcript of Bob's Blunders

Bob's Blunders
About the Author
Alla Pobsuk
Alla is currently a 6th grade student enrolled in Hyde Park Middle School's Magnet Program.

She excells in all subjects, especially mathamatics.
Question 1
The Question and Bob's answer:
If x = 3 and y = 2 then
xy = 32
What Bob did wrong:
In order to get 32, Bob combined 3 and 2. He forgot that two numbers next to each other means that you multiply. Therefore, he got 32.
The Solution and The Answer:
The way you were supposed to solve the problem is 3 times 2. The correct answer is 6.
Question 2
The Question and Bob's answer:
If x = 7, then 5x + 2 = 59
What Bob did wrong:
To get 59 Bob combined the two numbers to make one number. Bob forgot that 2 numbers next to each other means that you multiply.
The Solution and The Answer:
What you have to do is substitute x for 7. So, 5(7) + 2 = ? 5(7)= 35. 35 + 2= 37. the correct answer is 37.
Question 3
The Question and Bob"s answer:
If 8y = 2, then y = 4
What Bob did wrong:
To get y = 4, Bob did 8/4. Bob forgot that he was supposed to multiply the numbers. Two numbers next to each other means multiplication.
The Solution and The Answer:
What you have to do to get the right answer is take the expression, 8y = 2, in order to get the quality of y, you have to divide 8 into 2. Let's divide:
We get .25. So, y = .25. 8(.25) = 2
Question 4
The Question and Bob's answer:
"A negative value plus a positive value is _________," then the answer is always.
What Bob did wrong:
Bob's answer was always. He is wrong. He could have misread the problem to get his answer.
The Solution and The Answer:
The way your supposed to answer this question is to look at the possible outcomes of negative negative, positive positive, negative positive, and positive negative. Negative negative is positive, positive positive is positive, negative positive is a negative, and positive negative is a negative. So, the answer is sometimes.
Question 5
The Question and Bob's answer:
If the multiplication problem is (-9)(3), then the answer is -27
What Bob did wrong:
What Bob did to get -27, he multiplied, he was correct, but he forgot to watch his signs. Every time a negative multiplies by a negative, the answer is always positive.
The Solution and The Answer:
The correct way to solve this problem is to multiply -9 and -3, like Bob did, and see what sign was supposed to be used. So a negative times a negative will give you a positive. Therefore, your answer is a positive 27.
Question 6
The Question and Bob's answer:
If 3(a + 7) then the answer is 3a + 7
What Bob did wrong:
This question is asking you to simply the expression. So, Bob used distributive property. He did 3(a). But, he didn't distribute the 3 into 7. Therefore, he is wrong.
The Solution and The Answer:
So, what Bob did right was that he distributed 3 into a,
but he didn't distribute the 3 into the 7. If we distribute, we
get 21. So, the simplified version for this expression is 3a + 21.
Question 7
The Question and Bob's answer:
If a + 7 = -10, then 'a' = 3
What Bob did wrong:
Bob had the right number... but he didn't. He had the correct number-ish. he had a = 3. But, look at the answer. It says -10. NEGATIVE 10. So bob's answer is wrong.
The Solution and The Answer:
The correct way to solve this is to add 7 and 10, which will give you 17 and turn that 17 into a -17. -17 + 7 = -10, therefore, a = -17
Question 8
The Question and Bob's answer:
6y + 9 = 2, then 6y = 30 and y = 5
What Bob did wrong:
First, we take the y, which is 5, and multiply if by 6. You get 30. But, when you take 30 and add 9, you get 39 and not 21. Bob must have multiplied wrong.
The Solution and The Answer:
The right way to do this is first, take 21 and subtract 9. You want to do this because in order to find the value of y, you must take this and do it backwards. So, 21 - 9 = 12. Now, you have to see 6 and what number multiply to 12. The answer is, 6y = 12 and y = 2.
The Question and Bob's answer:
If given 15 + 6 ÷ 3 • 4 – 3, then the answer is 25
Question 9
What Bob did wrong:
This questions has to do with the order of operations. Bob didn't use the order of operations. He just did the equation the way it was written. left to right.
The Solution and The Answer:
The Correct way to answer this question is to use the order of operations, PEMDAS. The equation is 15 + 6 ÷ 3 • 4 – 3. What your going to do first is multiplication and division. So, we do whatever comes first (left to right) in the equation, division comes first. So, 6 ÷ 3 = 2. Re-Write the equation, 15 + 2 • 4 – 3. Now do the multiplication, 2 • 4. The answer is 8. Rewrite the equation again, 15 + 8 - 3. Just like the multiplication and the division, for the addition and subtraction, do the same thing, left to right, or whatever comes first. 15 + 8. That equals 23. Re-Write the equation once again. Now it's 23 - 3. Now subtract. The answer is 20.
Question 10
The Question and Bob's answer:
If x = 2, then x + 2x + 1 = 24
2
What Bob did wrong:
Bob forgot that two numbers next to each other means to multiply. Instead of getting 4 from 2x, he gets 22, then he adds and multiplies wrong
The Solution and The Answer:
The correct way to answer this question is to start by substituting x for 2. So, then the question would be: 2 + 2(2) + 1. Now solve the equation. 2 to the 2nd power is 4. Rewrite the question, 4 + 2(2) + 1. Now, what's 2(2)? 4. Rewrite the question again, 4 + 4 + 1. Then do the equation left to right. So , do 4 + 4, which is 8, then add that by 1. So the answer is 9.

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