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revisión puedo usar estrategias como descomponer los números o usar las…

Question

revisión
puedo usar estrategias como descomponer los números o usar las propiedades de la operación para hacer más fácil el cálculo mental. ¡dame magia ahora!
natalia tiene 372 botones. ella usó 14 botones para hacer un collar. ¿cuántos botones tiene magda ahora?
cambio hacia atrás
contar hasta 372
372 = 300 + 72
72 - 35 = 37
37 - 6 = 31
300 + 35 + 6 = 341
cuento hacia adelante
contar hasta 14
14 = 10 + 4
10 + 139 = 149
149 + 60 = 209
209 + 123 = 332
332 + 32 + 8 = 372
uso propiedades
puedo sumar 6 a 372 y a 14.
372 + 6 = 378
14 + 6 = 20
378 - 20 = 358
sumar la misma cantidad a cada número no cambia la diferencia.
haz 1 a 20, halla la diferencia usando el cálculo mental

  1. 232 - 117

232 + 1 = 233
-117 + 1 = ____

  1. 840 - 109

840 + 1 = ____
-109 + 1 = 110

  1. 201 - 112

201 + 8 = 209
-112 + 8 = ____

  1. 579 - 179

579 + 5 = ____
-179 + 5 = 200

  1. 456 - 177
  2. 781 - 536
  3. 229 - 119
  4. 647 - 335
  5. 153 - 37
  6. 777 - 125
  7. 841 - 283
  8. 976 - 918
  9. 809 - 413
  10. 604 - 405
  11. 543 - 132
  12. 975 - 242
  13. 480 - 255
  14. 460 - 312
  15. 800 - 325
  16. 799 - 428

Explanation:

To solve these subtraction problems using mental calculation (resta) with the property of adding the same number to both minuend and subtrahend (which doesn't change the difference), we'll go through each problem:

Problem 1: \( 232 - 117 \)
Step 1: Add 1 to both numbers.

\( 232 + 1 = 233 \)
\( 117 + 1 = 118 \)

Step 2: Subtract the new subtrahend from the new minuend.

\( 233 - 118 = 115 \)

Problem 2: \( 840 - 109 \)
Step 1: Add 1 to both numbers.

\( 840 + 1 = 841 \)
\( 109 + 1 = 110 \)

Step 2: Subtract the new subtrahend from the new minuend.

\( 841 - 110 = 731 \)

Problem 3: \( 201 - 112 \)
Step 1: Add 8 to both numbers.

\( 201 + 8 = 209 \)
\( 112 + 8 = 120 \)

Step 2: Subtract the new subtrahend from the new minuend.

\( 209 - 120 = 89 \)

Problem 4: \( 579 - 175 \)
Step 1: Add 5 to both numbers.

\( 579 + 5 = 584 \)
\( 175 + 5 = 180 \)

Step 2: Subtract the new subtrahend from the new minuend.

\( 584 - 180 = 404 \)

Problem 5: \( 656 - 177 \)
Step 1: Add 3 to both numbers (to make the subtrahend a multiple of 10? Alternatively, use direct subtraction).

\( 656 - 177 = 656 - 100 - 70 - 7 = 556 - 70 - 7 = 486 - 7 = 479 \)

Problem 6: \( 781 - 536 \)
Step 1: Subtract directly (or adjust with addition).

\( 781 - 536 = 781 - 500 - 30 - 6 = 281 - 30 - 6 = 251 - 6 = 245 \)

Problem 7: \( 229 - 119 \)
Step 1: Subtract the tens and ones directly (since the last two digits are the same).

\( 229 - 119 = (200 - 100) + (29 - 19) = 100 + 10 = 110 \)

Problem 8: \( 647 - 135 \)
Step 1: Subtract directly.

\( 647 - 135 = 647 - 100 - 30 - 5 = 547 - 30 - 5 = 517 - 5 = 512 \)

Problem 9: \( 153 - 17 \)
Step 1: Add 3 to both numbers to make the subtrahend a multiple of 10.

\( 153 + 3 = 156 \)
\( 17 + 3 = 20 \)

Step 2: Subtract.

\( 156 - 20 = 136 \)

Problem 10: \( 777 - 125 \)
Step 1: Subtract directly.

\( 777 - 125 = 777 - 100 - 20 - 5 = 677 - 20 - 5 = 657 - 5 = 652 \)

Problem 11: \( 841 - 283 \)
Step 1: Add 17 to both numbers to make the subtrahend a multiple of 100? (Alternatively, subtract directly).

\( 841 - 283 = 841 - 200 - 80 - 3 = 641 - 80 - 3 = 561 - 3 = 558 \)

Problem 12: \( 976 - 918 \)
Step 1: Subtract directly (focus on the last two digits).

\( 976 - 918 = (900 - 900) + (76 - 18) = 0 + 58 = 58 \)

Problem 13: \( 809 - 413 \)
Step 1: Subtract directly.

\( 809 - 413 = 809 - 400 - 10 - 3 = 409 - 10 - 3 = 399 - 3 = 396 \)

Problem 14: \( 604 - 405 \)
Step 1: Add 5 to both numbers to make the subtrahend a multiple of 10.

\( 604 + 5 = 609 \)
\( 405 + 5 = 410 \)

Step 2: Subtract.

\( 609 - 410 = 199 \)

Problem 15: \( 543 - 132 \)
Step 1: Subtract directly.

\( 543 - 132 = 543 - 100 - 30 - 2 = 443 - 30 - 2 = 413 - 2 = 411 \)

Problem 16: \( 975 - 242 \)
Step 1: Subtract directly.

\( 975 - 242 = 975 - 200 - 40 - 2 = 775 - 40 - 2 = 735 - 2 = 733 \)

Problem 17: \( 480 - 255 \)
Step 1: Add 5 to both numbers to make the subtrahend a multiple of 10.

\( 480 + 5 = 485 \)
\( 255 + 5 = 260 \)

Step 2: Subtract.

\( 485 - 260 = 225 \)

Problem 18: \( 460 - 212 \)
Step 1: Add 8 to both numbers to make the subtrahend a multiple of 10.

\( 460 + 8 = 468 \)
\( 212 + 8 = 220 \)

Step 2: Subtract.

\( 468 - 220 = 248 \)

Problem 19: \( 800 - 325 \)
Step 1: Add 75 to both numbers to make the subtrahend a multiple of 1000? Wait, better: \( 800 - 325 = 800 - 300 - 25 = 500 - 25 = 475 \)
Problem 20: \( 799 - 429 \)
Step 1: Subtract the last two digits (sin…

Answer:

s:

  1. \( \boldsymbol{115} \)
  2. \( \boldsymbol{731} \)
  3. \( \boldsymbol{89} \)
  4. \( \boldsymbol{404} \)
  5. \( \boldsymbol{479} \)
  6. \( \boldsymbol{245} \)
  7. \( \boldsymbol{110} \)
  8. \( \boldsymbol{512} \)
  9. \( \boldsymbol{136} \)
  10. \( \boldsymbol{652} \)
  11. \( \boldsymbol{558} \)
  12. \( \boldsymbol{58} \)
  13. \( \boldsymbol{396} \)
  14. \( \boldsymbol{199} \)
  15. \( \boldsymbol{411} \)
  16. \( \boldsymbol{733} \)
  17. \( \boldsymbol{225} \)
  18. \( \boldsymbol{248} \)
  19. \( \boldsymbol{475} \)
  20. \( \boldsymbol{370} \)