有Ｍａｔｈｓ題要問～(急!!)

Question

1./ The sum of three consecutive numbers is54. Find the three numbers.
2./ The sum of three consecutive even numbers is 42. Find the three numbers.
3./ The sum of three consecutive odd numbers is 81. Find the three numbers.
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THX~

Answer 1

Let the smallest number be x
1.
x + x +1 + x + 2 = 54
3x + 3 =54
3x = 51
x = 17
The three numbers are 17 , 18 , 19

2.
x + x + 2 + x + 4 = 42
3x + 6 = 42
3x = 36
x = 12
the three numbers are 12 , 14 , 16

3.
x + x + 2 + x + 4 = 81
3x + 6 = 81
3x = 75
x = 25
The three nunbers are 25 , 27 , 29

Answer 2

1)let z be the small number

z+z+1+z+2=54
3z+3=54
3z+3-3=54-3
3z=51
3z/3=51/3
z=17
所以the three consecutive number is 17,18,19

2)let z be the small even number

z+z+2+z+4=42
3z+6=42
3z+6-6=42-6
3z=36
3z/3=36/3
z=12
所以the three consecutive even number is 12,14,16

3)let z be the small odd number
z+z+2+z+4=81
3z+6=81
3z+6-6=81-6
3z=75
3z/3=75/3
z=25
所以the three consecutive odd number is 25,27,29

Answer 3

1) Let y be the smallest number
then y+1 and y+2 be the second larger and the largest numbers respectively
y+y+1+y+2=54
3y+3=54
3y=51
y=17
∴the required numbers are 17, 18 and 19 #

2) Let y be the smallest number
then y+2 and y+4 be the second larger and the largest numbers respectively
y+y+2+y+4=42
3y+6=42
3y=36
y=12
∴the required numbers are 12, 14 and 16 #

3) Let y be the smallest number
then y+2 and y+4 be the second larger and the largest numbers respectively
y+y+2+y+4=81
3y+6=81
3y=75
y=25
∴the required numbers are 25, 27 and 29 #

Answer 4

1) X - 1 + X + X + 1 = 54
3 X = 54
x = 18

2) X - 2 + X + X + 2 = 42
3 X = 42
X = 14

3) X - 2 + X + X + 2 = 81
3 X = 81
X = 27

Answer 5

第1題:17,18,19
第2題:13,14,15
第3題:25,27,29
啱晒--

Answer 6

1) 54=14+15+16

2) 42=12+14+16

3) 81=25+27+29

Answer 7

1)
x+(x+1)+(x+2)=54
3x=51
x=17
so, the three numbers are 17,18,19

2)
x+(x+2)+(x+4)=42
3x=36
x=12
so, the three numbers are 12,14,16

3)
x+(x+2)+(x+4)=81
3x=75
x=25
so, the three numbers are 25,27,29