SOLUTION: Stephen and Sara are brother and sister. Stephen has twice as many sisters as he has brothers. Sara has the same number of brothers as sisters. A)Set up a system of equations to m

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: Stephen and Sara are brother and sister. Stephen has twice as many sisters as he has brothers. Sara has the same number of brothers as sisters. A)Set up a system of equations to m      Log On


   

Question 598753: Stephen and Sara are brother and sister. Stephen has twice as many sisters as he has brothers. Sara has the same number of brothers as sisters.
A)Set up a system of equations to model this situation. How did you figure out what each equation would be? Let d be the number of daughters that Stephen and Sara's parents have, and s be the number of sons that Stephen and Sara's parents have.
B)How many sisters does Stephen have?
C)How many sisters does Sara have?
D)How many brothers does Stephen have?
E)How many brothers does Sara have?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
+s+ = number of Sons
Stephen is 1 of the Sons, so he has +s+-+1+ brothers
+d+ = number of daughters, which is number of sisters he has
given:
(1) +d+=+2%2A%28+s+-+1+%29+
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Sarah is one of the daughters, so she has
+d+-+1+ sisters
The number of her brothers is the number of Sons
given:
(2) +s+=+d+-+1+
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From (2),
(2) +d+=+s+%2B+1+
Substitute (2) into (1)
(1) +s+%2B+1+=+2s+-+2+
(1) +s+=+3+
and
(2) +d+=+s+%2B+1+
(2) +d+=+4+
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(B)
Stephen has +d+=+4+ sisters
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(C)
Sarah has +d+-+1+=+3+ sisters
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(D)
Stephen has +s+-+1+=+2+ brothers
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(E)
Sarah has +s+=+3+ brothers