Question

guided practice
do you understand?

1. when you place a 1 above the tens values, what does it mean?
2. when you place a 1 above the hundreds values, what does it mean?

do you know how?
find the sum by using partial sums and by using the standard algorithm.

1. 378

+ 557
find each sum using the strategy you choose.
4a. 678
+ 253
b. 325
+ 256
c. 185
+ 253

Explanation:

Step1: Explain placing 1 above tens

When placing a 1 above the tens values in addition, it means there is a carry - over of 1 ten (or 10) from the addition of the ones place values. For example, if 8 + 7 = 15 in the ones place, we write 5 in the ones place of the sum and carry 1 ten to the tens place.

Step2: Explain placing 1 above hundreds

When placing a 1 above the hundreds values in addition, it means there is a carry - over of 1 hundred (or 100) from the addition of the tens place values. For example, if 70+50 + the carried - over 10 = 130 in the tens place, we write 30 in the tens place of the sum and carry 1 hundred to the hundreds place.

Step3: Calculate 378+557 using partial sums

Break the numbers into parts: 378 = 300+70 + 8 and 557=500+50+7.
Sum the hundreds: 300 + 500=800.
Sum the tens: 70+50 = 120.
Sum the ones: 8 + 7=15.
Then add the partial sums: 800+120 + 15=935.
Using the standard algorithm:

  378
+ 557
-----
  935

Step4: Calculate 678+253

Using the standard algorithm:

  678
+ 253
-----
  931

Step5: Calculate 325+256

Using the standard algorithm:

  325
+ 256
-----
  581

Step6: Calculate 185+253

Using the standard algorithm:

  185
+ 253
-----
  438

Answer:

1. It means there is a carry - over of 1 ten from the addition of the ones place values.
2. It means there is a carry - over of 1 hundred from the addition of the tens place values.
3. 935 (using partial sums and standard algorithm)

4a. 931
4b. 581
4c. 438