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Anders and Petra and Karin are together 18 years old.Anders is half the age of Karin.Petra is half the age of Anders and Karin's age together.how old are the children?

Guest May 11, 2015

Best Answer 

 #1
avatar+26750 
+10

                                                                    A + P + K = 18      ...(1)

A = K/2          Multiply both sides by 2 to get  2A = K                   ...(2)

                                                                    P = (A + K)/2        ...(3)

 

Replace K in (1) and (3) using (2)

A + P + 2A = 18      or    3A + P = 18             ...(4)

P = (A + 2A)/2        or    P = 3A/2                  ...(5)

 

Replace P in (4) using (5)

3A + 3A/2 = 18      or 9A/2 = 18   so  9A = 36  or A = 4

 

Use A in (5) to get P = 3*4/2 or P = 6

 

Use A in (2) to get K = 2*4 or K = 8

 

Anders is 4, Petra is 6, Karin is 8

Alan  May 11, 2015
 #1
avatar+26750 
+10
Best Answer

                                                                    A + P + K = 18      ...(1)

A = K/2          Multiply both sides by 2 to get  2A = K                   ...(2)

                                                                    P = (A + K)/2        ...(3)

 

Replace K in (1) and (3) using (2)

A + P + 2A = 18      or    3A + P = 18             ...(4)

P = (A + 2A)/2        or    P = 3A/2                  ...(5)

 

Replace P in (4) using (5)

3A + 3A/2 = 18      or 9A/2 = 18   so  9A = 36  or A = 4

 

Use A in (5) to get P = 3*4/2 or P = 6

 

Use A in (2) to get K = 2*4 or K = 8

 

Anders is 4, Petra is 6, Karin is 8

Alan  May 11, 2015

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