Question 16

"Bella is more comfortable working with integers than with positive and negative decimal numbers. This is her way of understanding -4.3 + 2.5"

"-4.3 is -43/10 or -43 tenths.

25 is 25/10 or 25 tenths.

-43 tenths + 25 tenths is -18 tenths.

-18 tenths is -18/10 or -1.8.

So, -4.3 +2.5=1.8"

a) Use Bella's method to determine 6.1 + (-3.9)

6.1 is 61/10 or 61 tenths.

-3.9 is -3.9/10 or -39 tenths.

61 tenths + -39 tenths is 22 tenths

22 tenths is 22/10 or 2.2

Therefore, 6.1 + (-3.9) = 2.2

b) How could you modify Bella's method to determine 1.25 - 3.46?

You could multiply the decimal number by 10, 100, 1000... to make it into a whole number. Once you have found the difference/sum of the equation, then you could divide the difference/sum by 10, 100, 1000... to get it back into the right decimal place.

eg. 1.25 - 3.46

1.25x100=125

3.46x100=346

125-346=-221

-221/100=-2.21

Therefore, 1.25-3.46= -2.21