Today John is 10 years old.
John was asked about his age, and he answered:
20 years ago my grandmother was 2 times older than my mother. Today,
my grandmother is 2 times older then my mother was when I was born.
How old is John?
20 years ago my grandmother was 2 times older than my mother. Today,
my grandmother is 2 times older then my mother was when I was born.
How old is John?
Solution:
X - Mother’s age
Y - Grandmother’s age
Z - John’s age today
X - 20 - Mother’s age 20 years ago
Y - 20 - Grandmother’s age 20 years ago
Y - 20 = 2(x - 20) <=> Y = 2x - 20
Today, my grandmother is 2 times older then my mother was when I was born.
Y = 2(x -20 + z) <=> 2x - 20 = 2x - 40 + 2z
-20 = -40 +2z
20 = 2z
Z = 10
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