Mental addition and subtraction by adjusting (99, 199, 101…)

Question 1

374 + 98 = ?

Answer 

Question 2

Ethan works out 374 − 99 by doing 374 − 100 = 274, then subtracting 1 more to get 273. What should Ethan have done, and what is 374 − 99?

Answer 

Question 3

796 + 199 = ?

Answer 

Question 4

Ava works out 539 − 99 by doing 539 − 100 = 439, then subtracting 1 more to get 438. What should Ava have done, and what is 539 − 99?

Answer 

Question 5

425 − 199 = ?

Answer 

Question 6

Ava works out 809 − 99 by doing 809 − 100 = 709, then subtracting 1 more to get 708. What should Ava have done, and what is 809 − 99?

Answer 

Question 7

150 − 99 = ?

Answer 

Question 8

Daniel works out 269 − 99 by doing 269 − 100 = 169, then subtracting 1 more to get 168. What should Daniel have done, and what is 269 − 99?

Answer 

Question 9

246 + 199 = ?

Answer 

Question 10

Sofia works out 384 − 99 by doing 384 − 100 = 284, then subtracting 1 more to get 283. What should Sofia have done, and what is 384 − 99?

Answer 

Question 11

516 + 299 = ?

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Question 12

Aisha works out 315 − 99 by doing 315 − 100 = 215, then subtracting 1 more to get 214. What should Aisha have done, and what is 315 − 99?

Answer 

Question 13

235 + 299 = ?

Answer 

Question 14

Priya works out 855 − 99 by doing 855 − 100 = 755, then subtracting 1 more to get 754. What should Priya have done, and what is 855 − 99?

Answer 

Question 15

800 + 199 = ?

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Question 16

Nia works out 601 − 99 by doing 601 − 100 = 501, then subtracting 1 more to get 500. What should Nia have done, and what is 601 − 99?

Answer