Adding and Subtracting Within 1,000: math test solutions, Grade 3 – download the PDF

1 Mental math / 4 pts

1. \(360 + 280 = 640\) (1 pt)
2. \(800 - 350 = 450\) (1 pt)
3. \(399 + 125 = 400 + 125 - 1 = 524\) (1 pt)
4. \(700 - 298 = 700 - 300 + 2 = 402\) (1 pt)

2 Standard algorithm: addition / 3 pts

1. \[\begin{array}{r} 456 \\ +\;278 \\ \hline 734 \end{array}\]\(456 + 278 = 734\) (1 pt)
2. \[\begin{array}{r} 385 \\ +\;497 \\ \hline 882 \end{array}\]\(385 + 497 = 882\) (1 pt)
3. \[\begin{array}{r} 249 \\ +\;356 \\ \hline 605 \end{array}\]\(249 + 356 = 605\) (1 pt)

3 Standard algorithm: subtraction / 4 pts

1. \(862 - 437 = 425\) (1 pt)
2. \(540 - 276 = 264\) (1 pt)
3. \(700 - 418 = 282\) (1 pt)
4. \(913 - 575 = 338\) (1 pt)

4 Estimate and check / 3 pts

1. \(487 \approx 500\) and \(312 \approx 300\), so the estimate is \(500 + 300 = 800\). (1 pt)
2. \(487 + 312 = 799\). (1 pt)
3. \(799 - 312 = 487\), which is the first number, so the sum is correct. (1 pt)

5 Word problems / 4 pts

1. Add: \(468 + 397 = 865\). (1 pt) The zoo had 865 visitors in all. (1 pt)
2. Subtract: \(920 - 548 = 372\). (1 pt) The farmer has 372 eggs left. (1 pt)

6 Find the error / 2 pts

Sam subtracted the smaller digit from the larger one in each column (\(8 - 5 = 3\), \(6 - 0 = 6\), \(4 - 1 = 3\)) instead of regrouping. (1 pt)

The correct answer is \(405 - 168 = 237\). (1 pt)