Answer :
A) Sally’s statement is sometimes true. The equations students write to support their answers will vary. Sample pairs of equations that support the answer “sometimes true” are as follows:
Sample addition equation:–6.2 + 5.71 = –0.49Sample subtraction equation:–3.96 – 2.84 = –6.8
B) You can always change the order of positive and negative decimals when adding and you’ll get the same answer. When you change the order of positive and negative decimals when subtracting, you will get opposite answers.
C) Sally’s statement is true for addition of three positive and negative decimals but not true for subtraction. The equations students write to support their answers will vary. Sample pairs of equations that support the answer that Sally’s statement is true for addition but not subtraction are as follows:
Sample addition equation:
–6.2 + 5.71 + (–3.96) = –4.45Sample subtraction equation:2.84 – (–3.96) – (–6.2) = 13
Sample addition equation:–6.2 + 5.71 = –0.49Sample subtraction equation:–3.96 – 2.84 = –6.8
B) You can always change the order of positive and negative decimals when adding and you’ll get the same answer. When you change the order of positive and negative decimals when subtracting, you will get opposite answers.
C) Sally’s statement is true for addition of three positive and negative decimals but not true for subtraction. The equations students write to support their answers will vary. Sample pairs of equations that support the answer that Sally’s statement is true for addition but not subtraction are as follows:
Sample addition equation:
–6.2 + 5.71 + (–3.96) = –4.45Sample subtraction equation:2.84 – (–3.96) – (–6.2) = 13