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

@ganeshie8

Answer 1

do you see any mistakes yet ?

Answer 2

umm.. i dont get it

Answer 3

i see one mistake, look at 4th and 5th lines

Answer 4

-11.8 + 9.8 = ?

Answer 5

its right.

Answer 6

its -21.6

Answer 7

how ?

Answer 8

because -11.8 + 9.8 is -21.6

Answer 9

right?

Answer 10

nope

Answer 11

suppose :

you owe me $11.8
and you have $9.8

Answer 12

whats you net financial position ?

Answer 13

it would be -$2 right ?

Answer 14

yes

Answer 15

you're still lacking $2 to clear my debt

Answer 16

similarly

-11.8 + 9.8 evaluates to -2
and not -21.6

Answer 17

oh ok.

Answer 18

think of "negative numbers" as debt to be paid
and "positive numbers" as money in ur pocket

Answer 19

ok

Answer 20

see if u can explain the mistake..

Answer 21

umm.. i dont know

Answer 22

You may start like this :

There is a mistake in the 5th step while simplifying `-11.8 + 9.8`. Andrew did the addition instead of subtraction...

Answer 23

oh ok.

Answer 24

is that the only mistake there is.

Answer 25

@ganeshie8