SOLUTION: A girl is half as old as her brother and two years younger than her sister.the sum of the age of the three children is 34 years.how old is each child?

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Question 625087: A girl is half as old as her brother and two years younger than her sister.the sum of the age of the three children is 34 years.how old is each child?
Answer by Maths68(1474) About Me  (Show Source):
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Let
Present age of the girl=g years old
Present age of the brother=b years old
Present age of the sister=s years old

Girl is half as old as her brother
g=b/2
2g=b
b=2g.............(1)
and two years younger than her sister
g=s-2
g-s=-2.............(2)
The sum of the age of the three children is 34 years
g+b+s=34..........(3)
Put the value of b from (1) to (3)
g+b+s=34
g+2g+s=34
3g+s=34............(4)
Multiply (2) by -3 and add to (4)
3g+s=34
-3g+3s=6
---------------
4s=40
Divide by 4 both sides of the above equation
4s/4=40/4
s=10
Put the value of s in (2)
g-s=-2.............(2)
g-10=-2
g=-2+10
g=8
Put the value of g in (1)
b=2g.............(1)
b=2(8)
b=16

Present age of the girl=g=8 years old
Present age of the brother=b=16 years old
Present age of the sister=s=10 years old