Decompose the numbers
What is 263 + 149 decomposed into friendly numbers?
answers many vary : ex could be
263 --> 260 (-3)
149 ---> 150 (+1)
260 + 150 = 410
(need to add back the -3) 410+3 = 413
then I need to take away the (+1 because we added an extra number to make it friendly)
413-1= 412
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 ----> 60 (+3)
38 ----> 40 (+2)
60 + 40 = 100
100 - 3 = 97
97 - 2 = 95
Solve 300 - 145 using friendly numbers.
300
145 ---> 150 (+5)
300 + 150 = 450
450-5 = 445
Re-write this to make it a friendly number equation 450 + 275 =
450 --- 450
275 --- 280 (+5)
450 + 280 - 5=
What is 486-224 decomposed into friendly numbers?
486 ----> 490 (+4) ----> 500 (+10)
224 ----> 220 (-4) ----> 200 (-20)
500+200= 700
full equation 500+200-4-10+4+20= 710
Give me any friendly number?
1, 5, 10, 25, 100
Solve with friendly numbers: 124 + 56 =
124 ----> 120 (-4) ----> 100 (-20)
56 ----> 50 (-6)
120+50 = 170
170+4 = 174
174+20 = 194
194 + 6= 200
Solve using friendly numbers/decomposing: 500-236=
500 ---> 500
236 ---> 230 (-6) ---> 200 (-30)
500 + 200 = 700
700 + 6 = 706
706 + 30 = 736
675 ---> 680 (+5) ---> 700 (+20)
289 ---> 300 (+11)
What is 715 + 198 decomposed?
715 ---> 700 (-15)
198 ---> 200 (+2)
Give an example of two friendly number that add to 50?
example.
30+20
25+25
40+10
Solve: 134 + 67= using friendly numbers.
134 ---> 130 (-4)
67 ---> 70 (+3)
130+70= 200
200+4 = 204
204-3 = 201
Solve: 800 - 278 = using decomposition
800 ---> 800
278 ---> 280 (+2)
800 - 280 = 520
520 + 2 = 522
What is the fastest way to calculate 937 - 485?
answers may vary
512 ---> 510 (-2)
367 ---> 370 (+3)
510 - 370 + 2 - 3=
ex. 90, 95, 105
Solve 213+89= using decomposition.
213 ---> 210 (-3)
89 ---> 90 (+1)
210 + 90 = 300
300 +3 = 303
303 - 1 = 302
Solve 900 - 432 = using friendly numbers
900 ---> 900
432 ---> 430 (-2)
900+430 = 1330
1330 + 2 = 1332
How would you break down 999 - 456 =
answers may vary
What is 845 - 378 decomposed into friendly numbers?
845 ----> 850 (+5)
378 ----> 380 (+2) ---> 400 (+20)
850 + 400 + 5 + 2 + 20 =
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 ---> 250 (+5)
376 ---> 380 (+4) ---> 400 (+20)
400+250 = 650
650 - 5 = 645
645 - 20 = 625
625 - 4 = 621
Solve 650 - 299 = using friendly numbers
650 ---> 650
299 ---> 300 (+1)
650 - 300 = 950
950 -1 = 949
answers my vary