Add & Subtract Using the Standard Algorithm

"I used mental math because 599 is close to 600. 600 + 64 = 664."

400 + 50 + 6

Yes, you need to regroup, since 432 only has 2 ones. 129 has 9 ones.

Yes, 5 ones + 7 ones equals 12 ones or 1 tens and 2 ones.

567 = 500 + 67 and 345 = 300 + 45. The difference is 500 – 300 = 200 plus 67 – 45 = 22, which is greater than 200.

1) Stack the numbers vertically by place value.
2) Add together the numbers that share the same place value, beginning in the ones column.
3) Write the sum below each column.
4) If the sum in a column is greater than 9, regroup.

1) Stack the numbers vertically by place value with the first number on top.
2) Subtract the numbers that share the same place value, beginning in the ones column.
3) Write the difference below each column.
4) If the top number in a column is less than the bottom number, regroup before subtracting.

He is incorrect. He added 3 + 8 = 11 in the ones place and put a 1 in the ones column but forgot to regroup 10 ones to 1 ten in the tens place.

She is incorrect. She subtracted the smaller number from the bigger number in each column, not the bottom number from the top.

Yes, the standard algorithm can be used for any addition or subtraction problem.