How to do Scratch Addition

1
How to do Scratch Addition

• By
• Norene Nelson

2
Step One

• First, you take an addition problem such as
  573641 X
• You set the problem up in example

57 36 41 X
3
Hidden Slide
awesome
4
Step Two

• You need to regroup the ones place and trade it
  for a ten.
• To do so you add all the ones digits and replace
  them with a scratch to represent the tens. In
  example

57 36 41
3
5
Example of step two

• You first add the 7 and the 6. This equals 13 so
  you record the 3 out to the side.
• You then trade the 10 that you have left over for
  a scratch and you scratch through the 6.
• You then proceed to add the 3 and the 1 giving
  you 4
• You record the 4 at the bottom where the sum
  goes.

57 36 41
76 13
3
314
4
6
Step Three

• Adding the tens place is the next step
• First you carry the number of scratches made
  above the top number in the tens place.
• Next you add that number to the next number in
  the tens place.
• If you have a number that is a double digit you
  make a scratch through the bottom number you are
  adding and record the number that would be in the
  ones place.
• In example

7
Example of step two

• First , you add the 1 and 5. the answer is six so
  you do not have to regroup.
• You then add the 6 and 3 once again no need to
  regroup
• Last you add the 9 and 4 this gives 13 and there
  is need for regrouping which will be shown in the
  next slide. So you record the 3 and scratch the
  four.

1
57 36 41 4
516
6
639
9
9413
3
8
Step Four

• In step four you are taking the one hundreds
  scratch and applying it to the answer.
• Because you have a scratch you will regroup the
  tens that you scratched through for a one
  hundreds place.

9
Example of Step Four
1
101

• You carry the scratch that you made in the tens
  spot over to the one hundreds spot.
• Because there are no numbers in the 100s spot
  you place zeros there to hold the spot
• You then add you number of scratches to the
  zeros giving you the sum of the problem.

057 036 041 34
1
101
1
101
1
10
Checking Your Problem

• To check your problem you should just solve the
  problem the traditional way.
• If your problem is wrong you should rework the
  problem carefully.
• For more information about math please visit
  http//tiger.towson.edu/mlackn1/mathwebsitestuden
  t1.htm