Question

Andrew is showing his work in simplifying −4.5 + 4.2 + 5.6 − 7.3. Identify any errors in his work or in his reasoning. Write feedback to Andrew explaining the mistake he made and how to correct his work.

Step Work Reasoning
−4.5 + 4.2 + 5.6 − 7.3 Original problem
1 −4.5 + 4.2 + 5.6 + (−7.3) Additive inverse
2 −4.5 + (−7.3) + 4.2 + 5.6 Commutative property
3 (−4.5 + (−7.3)) + (4.2 + 5.6) Associative property
4 −11.8 + 9.8 Simplify
5 −21.6 Simplify

Answer 1

okay so look at the last part

instead of it being -2 he made it -21.6

Answer 2

ok

Answer 3

do you get it ? or do you need more explaining?

Answer 4

how do i correct it?

Answer 5

it would be simplifying but instead of -21.6 its -2

Answer 6

Oh thank you :D

Answer 7

Step 4: -11.8 + 9.8
You need to add a negative number (-11.8) to a positive number (9.8)
Do you know how to add a positive number and a negative number?

Answer 8

no

Answer 9

thanks for your help rebecca :D

Answer 10

math student its -21.6

Answer 11

This is how you do it.

Adding a positive and a negative number.

First, take both numbers, and get rid of the signs.
Think simply of 11.8 and 9.8

Now subtract the way you learned to subtract in elementary school before you learned negative numbers.
That means, subtract the smaller one from the larger one.
11.8 - 9.8 = 2

Now look again at the original numbers. The final answer has the same sign as the larger number (without the signs).
Since 11.8 is larger than 9.8, the answer has the same sign as 11.8 has which is -11.8, so a negative sign.
The answer is negative, so the answer is -2.

Answer 12

Thank you

Answer 13

The mistake was from step 4 to step 5.
-11.8 + 9.8 = -2, not -21.6

Answer 14

You're welcome.