Decompose the numbers
What is 263 + 149 decomposed into friendly numbers?
263 - 200, 60, 3 (or stay the same)
149 - 100, 40, 9
What is a friendly number?
ex. A friendly number is a number that is easy to work with when solving math problems. For example, numbers like 10, 20, 50, 100, or 1,000 are friendly because they make adding and subtracting
Solve: 57 + 38 with friendly numbers.
57 ----> 57
38 ----> 30 and 8
57 + 30 = 87
87+8 = 95
Solve 300 - 145 using friendly numbers.
300 --- (stay the same)
145 --- 100, 40,5
300 - 100 = 200
200 - 40 = 160
160 - 5 = 155
Re-write this to make it a friendly number equation 450 + 275 =
400 + 200 + 50 + 70 + 0 +5 =
What is 486-224 decomposed?
486 (stay the same)
224 - 200, 20, 4
Give me any friendly number?
1, 5, 10, 20, 100
Solve with friendly numbers: 124 + 56 =
124 ---> 100, 20, 4
56 ----> 50, 6
100 + 0 = 100
20 + 50 = 70
4 + 6 = 10
100 + 70 + 10 = 180
Solve using friendly numbers/decomposing: 500-236=
500 ----> stay the same
236 ----> 200, 30, 6
500-200 = 300
300 - 30 = 270
270 - 6 = 264
How do you break down 675 - 289
675 ---> 600, 70, 5
289 ---> 200, 80, 9
What is 715 + 198 decomposed?
715 - 700, 10, 5 (or stay the same)
198 - 100, 90, 8
Give an example of two friendly number that add to 50?
example.
30+20
40+10
Solve: 134 + 67= using friendly numbers.
134 ---> 100, 30, 4
67 ---> 60, 7
100 + 0 = 100
60 + 30 = 90
4 + 7 = 11
100 + 90 = 200
200 +11 = 211
Solve: 800 - 278 = using decomposition
800 ---> 800
278 ---> 200, 70, 8
800- 200 = 600
600 - 70 = 530
530 - 8 = 522
What is the fastest way to calculate 937 - 485?
answers may vary
What is 512 + 367 decomposed into friendly numbers?
512 - 500, 10, 2 (or can stay the same)
367 - 300, 60, 7
1000
300
40
5
Solve 213+89= using decomposition.
213 ---> 200, 10, 3
89 ---> 80, 9
200 + 0 = 200
10 + 80 = 90
3 + 9 = 12
200 + 90= 290
290 + 12= 302
Solve 900 - 432 = using friendly numbers
900 ---> 900
432 ---> 400, 30, 2
900 - 400 = 500
500 - 30 = 470
470 - 2 = 468
How would you break down 999 - 456 =
999 ---> 900, 90, 9
456 ---> 400, 50, 6
What is 845 - 378 decomposed into friendly numbers?
845 - 800, 40, 5 (or stay the same)
378 - 300, 70, 8
How do friendly numbers help in mental math?
example answer:
Friendly numbers help in mental math by making calculations easier and faster. They are numbers that are simple to work with because they follow patterns like being multiples of 10, 50, or 100. Using friendly numbers allows you to solve math problems in your head without needing paper or a calculator.
Solve 245 + 376= using decomposition
245 ---> 200, 40, 5
376 ---> 300, 70, 6
200 + 300 = 500
40 + 70 = 110
5 + 6 = 11
500 + 110 = 610
610 + 11 = 621
Solve 650 - 299 = using friendly numbers
650 ---> 600, 50
299 ---> 200, 90, 9
600 - 200 = 400
90 - 50 = 40
9 - 0 = 9
400 - 40 = 360
360 - 9 = 351
Solve 1,123 - 678 mentally?
1000 - 0 = 1000
600 - 100 = 500
70 - 20 = 50
8 - 3 = 5
1000 - 500 = 500
500 - 50 = 450
450 - 5 = 445