Grandparents 5675

Susan asked her grandmother how many years had passed since her wedding to her grandfather. The grandmother replied that she has been married for 2/3 of her life and that her grandfather, who is 12 years older than her, has been married for 6/11 of his life.

How old are Suzan's grandparents? How many years have passed since their wedding?

Correct answer:

b =  54
d =  66
s =  36

Step-by-step explanation:


d = 12 + b
2/3 b = s
6/11 d = s

d = 12 + b
2/3·b = s
6/11·d = s

b-d = -12
2b-3s = 0
6d-11s = 0

Pivot: Row 1 ↔ Row 2
2b-3s = 0
b-d = -12
6d-11s = 0

Row 2 - 1/2 · Row 1 → Row 2
2b-3s = 0
-d+1.5s = -12
6d-11s = 0

Pivot: Row 2 ↔ Row 3
2b-3s = 0
6d-11s = 0
-d+1.5s = -12

Row 3 - -1/6 · Row 2 → Row 3
2b-3s = 0
6d-11s = 0
-0.333s = -12


s = -12/-0.33333333 = 36
d = 0+11s/6 = 0+11 · 36/6 = 66
b = 0+3s/2 = 0+3 · 36/2 = 54

b = 54
d = 66
s = 36

Our linear equations calculator calculates it.



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