Explanation:
To solve this task, we need to estimate sums and differences by rounding each number to the nearest ten. Here's how to do it step by step:
1. Look at the ones digit of each number.
- If the ones digit is 5 or more, round up to the next ten.
- If the ones digit is 4 or less, round down to the previous ten.
2. After rounding both numbers, add or subtract them to get the estimated sum or difference.
Let’s go through each problem:
1) 936 + 438
- 936 → 940 (because 6 ≥ 5, round up)
- 438 → 440 (because 8 ≥ 5, round up)
- 940 + 440 = 1380
✔ Answer: 1380
2) 498 - 183
- 498 → 500 (because 8 ≥ 5, round up)
- 183 → 180 (because 3 ≤ 4, round down)
- 500 - 180 = 320
✔ Answer: 320
3) 542 - 244
- 542 → 540 (because 2 ≤ 4, round down)
- 244 → 240 (because 4 ≤ 4, round down)
- 540 - 240 = 300
✔ Answer: 300
4) 827 - 792
- 827 → 830 (because 7 ≥ 5, round up)
- 792 → 790 (because 2 ≤ 4, round down)
- 830 - 790 = 40
✔ Answer: 40
5) 914 + 746
- 914 → 910 (because 4 ≤ 4, round down)
- 746 → 750 (because 6 ≥ 5, round up)
- 910 + 750 = 1660
✔ Answer: 1660
6) 616 - 454
- 616 → 620 (because 6 ≥ 5, round up)
- 454 → 450 (because 4 ≤ 4, round down)
- 620 - 450 = 170
✔ Answer: 170
7) 369 + 159
- 369 → 370 (because 9 ≥ 5, round up)
- 159 → 160 (because 9 ≥ 5, round up)
- 370 + 160 = 530
✔ Answer: 530
8) 777 - 466
- 777 → 780 (because 7 ≥ 5, round up)
- 466 → 470 (because 6 ≥ 5, round up)
- 780 - 470 = 310
✔ Answer: 310
9) 226 + 526
- 226 → 230 (because 6 ≥ 5, round up)
- 526 → 530 (because 6 ≥ 5, round up)
- 230 + 530 = 760
✔ Answer: 760
10) 949 + 123
- 949 → 950 (because 9 ≥ 5, round up)
- 123 → 120 (because 3 ≤ 4, round down)
- 950 + 120 = 1070
✔ Answer: 1070
11) 839 - 342
- 839 → 840 (because 9 ≥ 5, round up)
- 342 → 340 (because 2 ≤ 4, round down)
- 840 - 340 = 500
✔ Answer: 500
12) 836 + 845
- 836 → 840 (because 6 ≥ 5, round up)
- 845 → 850 (because 5 ≥ 5, round up)
- 840 + 850 = 1690
✔ Answer: 1690
13) 458 + 467
- 458 → 460 (because 8 ≥ 5, round up)
- 467 → 470 (because 7 ≥ 5, round up)
- 460 + 470 = 930
✔ Answer: 930
14) 784 - 395
- 784 → 780 (because 4 ≤ 4, round down)
- 395 → 400 (because 5 ≥ 5, round up)
- 780 - 400 = 380
✔ Answer: 380
Final Answer:
1) 1380
2) 320
3) 300
4) 40
5) 1660
6) 170
7) 530
8) 310
9) 760
10) 1070
11) 500
12) 1690
13) 930
14) 380
Parent Tip: Review the logic above to help your child master the concept of addition estimation worksheet 2nd.
