덧셈과 뺄셈 문제풀이

덧셈과 뺄셈 문제풀이

1) (-7) + (+12) - (-8) =

+(12-7) +(+8) =

5+8 = 13

 

2) (+4/3) - (-1/5) + (+6/5) + (-2/3) =

+(4/3 – 2/3) + (+1/5)+(6/5) =

2/3 + 7/5 = 10/15 + 21 / 15 =

31/15

 

3) (-5) + (+7) - (-3) - (+4) =

+(7-5) + (+3) + (-4) =

(+2) + (+3) + (-4) = (5-4) = 1

 

4) (+3/4) + (-1/3) - (-1) =

(+9/12) + (-4/12) + (12/12) =

(9-4+12)/12 = 17/12

 

 

1) 5 + 16 – 14 =

21-14 = 7

 

2) -15 + 2 + 13 – 8 =

-15 + (2+13) – 8 =

-15 +15 – 8 = -8

 

3) 9 - 11 + 3 =

-(11-9) + 3 =

-2 + 3 = 1

 

4) -2 + 3 + 5 – 7 =

-(2+7) + (3+5) =

-9 + 8 = -1

 

5) 2/3 + 1/5 - 1/2 =  통분하기위하여 2,3,5의 최소공배수 : 30

20/30 + 6/30 =

15/30 =

(20+6-15) / 30 = 11/30

연습문제 정답

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