please help with these math problems!

Question

Read the question carefully. Type your question in the box below. Be sure to answer ALL parts.

Mrs. Stanley’s students are working on math problems. Mrs. Barrett has put two problems on the board for the students to work on.

Part A: Johanna does the following problem incorrectly. Explain the error and redo the problem showing the correct answer.



Johanna’s Answer

-1.2 – 0.5 = -0.7



Part B: Mrs. Stanley gives the following problem: “What is -0.5 reduced by –0.2?” Two students show their work below. Michael says that both he and Joshua are correct since –0.5 minus –0.2 is the same as –0.2 minus –0.5. Are both students correct? If not, say who is correct and explain your answer.



Joshua’s Answer         Michael’s Answer

-0.5 – (-0.2)                -0.2 – (-0.5)

= -0.5 + 0.2 =              -0.2 + 0.5

= -0.3                           = 0.3

 

- 0.5 reduced by - 0.2 That tells you that the equation is to start with the -0.5, so that would make Joshua's own answer correct, for now. It tells you to reduce by a negative number - "reduce" and "negative" together means "minus a minus" which is the same as "plus a plus" so when Joshua changes "- -0.2" to " + 0.2," his own answer is still correct. Joshua's own answer is correct, but he's not correct if he says both answers are the same. Micheal sets up the wrong equation, his solution to that equation is correct, but it's not the equation he was supposed to do.

Answer 1

For part A remember that subtraction can always be rewritten as addition of the negative. Therefore:

 

- 1.2 - 0.5

is equvalent to

 -1.2 + (-0.5)

which equals -1.7.

 

 

Joanna, however, adds 0.5 to -1.2 which equals -0.7, which is an incorrect answer for -1.2 - 0.5

 

 

For part B what you have written (repeated below) is the correct answer.

 

"- 0.5 reduced by - 0.2 That tells you that the equation is to start with the -0.5, so that would make Joshua's own answer correct, for now. It tells you to reduce by a negative number - "reduce" and "negative" together means "minus a minus" which is the same as "plus a plus" so when Joshua changes "- -0.2" to " + 0.2," his own answer is still correct. Joshua's own answer is correct, but he's not correct if he says both answers are the same. Micheal sets up the wrong equation, his solution to that equation is correct, but it's not the equation he was supposed to do."