Mental Math
198 + 583
When solving with mental math, if I add 2 to 198 to make it 200, what do I have to do with the 583?
Subtract 2
198 + 583
+2 -2
200 + 581 = 781
49 + 156
200
97 - 48
50
There are 167 books in one classroom and 392 books in the other. How many books are there altogether in both classrooms?
According to the library system, there are 238 new patrons, 145 inactive patrons and 673 active patrons. How many patrons are there in total in the library system?
238 + 145 + 673
876 - 304
When solving with mental math, if I subtract 4 from 304 to make it 300, what do I have to do with the 876?
Subtract 4
876 - 304
-4 -4
872 - 300 = 572
503 + 192
700
153 - 27
120
Jenny has $5.60. She spends $2.80 on a present for her brother. How much money does she have left?
Subtraction
Felix wants 156 cupcakes for his party. Felix has already made 48 berry cupcakes, and 72 vanilla cupcakes. How many more cupcakes does Felix need to make?
156 - 48 - 72
or
48 + 72 = x and 156 - x
How might you break up these numbers to add them more easily?
68 + 52
Break up the 52 into 50 and 2, and add the 2 to turn 68 into 70
1 322 + 2 685
4 000
1 615 - 389
1 200
18 children were on a school bus. More children got on at the next stop. There were not 25 children on the bus. How many children got on the bus?
Subtraction
Kendall milks her Holstein cows twice a day. This morning she got 365 litres of milk. This evening she got 380 litres. She sold 612 litres to the local ice cream factory. How many gallon of milk does she have left?
365 + 380 - 612
What mental math strategy might cause you to visualize a number line?
Counting Up or Counting Down
12 306 + 2 765
15 000
10 234 - 866
9 300 or 9 100
Mary likes to collect coins. Mary got 21 coins from her brother, 30 coins from her mother, as well as 33 coins from Mike. However, Mary lost 34 coins before putting those coins into her piggybank. How many coins does Mary have in her piggybank?
Addition and Subtraction
Karman uploaded his music video which had 264 views and 54 reactions during its first week. The video gained 405 more viewers during the second week. After its third week, the video had a total of 1,052 views. How many views were there in week 3?
1 052 - 264 - 405
OR 264 + 405 = x and 1052 - x
1 462 - 398
1 064
102 544 + 63 900
160 000 or 167 000
197 000 - 53 126
144 000 or 150 000
Scarlet bought a sketch book with 125 blank pages in it. She tears out 7 blank pages for her friend to draw on. Scarlet draws pictures on 64 pages. How many blank pages does she have left in the sketch book?
Subtraction or Addition and Subtraction
Before getting to school, Sahib has a few errands to run. Sahib has to walk 10 blocks to the store, and 5 blocks to the gallery, before walking the final 9 blocks to arrive at school. If Sahib has already walked 7 blocks, how many more blocks must he walk before arriving at school?
10 + 5 + 9 - 7