Adding and Subtracting decimals!

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Adding and Subtracting decimals!

• Mr. Vachon says, If you can carry, borrow, and
  line up place values I bet you can add and
  subtract decimals as fast as a jack rabbit!

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Remember that for our lessons
Is 0.1 Or 1/10 Like a dime!
Is 0.01 Or 1/100 Like a penny!
Is 1 whole Like a dollar!
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Remember when we add decimals, its not very
different than adding regular numbers.




0.45
0.26
Mr. Vachon says, First combine your hundredths!
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Lets get to it!
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0.4 5 0.2 6
0.
1
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1st Put together your hundredths 2nd If there
are more than 10 of them, regroup and adjust 3rd
Put together your tenths 4th If you have
10/10 then youve made one wholeDo We?
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Lets visually see what happens when we need to
borrow while subtracting decimals
0.61 -0.25
__
0.61
0.25

How can we possibly take .05 away from .01 ?
asked the confused student. Well just have to
borrow like we always do, said the teacher.
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Looks like its time to borrowHeres what were
actually doing
0.6 (1) -0.2 5
First we need to subtract our hundredthsbut
there arent enough! whined the students. Looks
like well have to borrow from one of those big
tenths, said Mr. Vachon smugly.
Break one of those tenths (rods) into hundredths
(cubes) and the problem will be very easy.
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Lets Get To It!
0.5 (11) -0.2 5
0. 3 6
Now that weve already borrowed, and regrouped
from the tenths, what are we left with? 1st
Start one the far right, with the hundredths. 2nd
Subtract 0.05 (five hundredths) from 0.01 (one
Hundredth) 3rd Now subtract 0.2 (2 tenths) from
0.5Whats left? 4th Any whole ones to deal
with?