What is the “Old Math” that our parents and grandparents did, and what does it involve doing that’s different than the “New Math”?

Question

Specifically the addition and subtraction part of it.

In: 19

Answer 1

Pardon the lack of formatting. I’m on mobile, and I’m not fluent in reddit yet.

Say you wished to add 789 three times.
You’d write:

789

789

+789

—-

Add the three 9s and you get 27. Bring down the 7, put 2 at the top of the next column.

2

789

789

+789

—-

7

Add the three 8s plus the 2 and you get 26. Bring down the 6, put the 2 at the top of the next column.

22

789

789

+789

—-

67

Add the three 7s plus the 2 and you get 23. Since there is no other column, bring the whole thing down and you are at 2367.

For subtraction, let’s say you have 951 minus 762. You’d write:

951

-762

—-

You’d subtract the first columns. 9-7=2. Easy peasy.

951

-762

—-

2

Now, you can’t subtract 6 from 5 because 6 is larger than 5, so now you have to borrow 10 from the 2 from the previous step, and now you have 15-6 = 9.

9 15 1

-7 6 2

– – – – – –

1 9

You’re left with 1 minus 2 which isn’t allowed, so you have to borrow again, but I think you understand how the rest works.