Mary who is sixteen years old is four times as old as her brother.How old will mary be when his twice as old as her old brother?
Let the brother's age be x:
16years for Mary = 4x years for Brother
From equation: 4x = 16
x = 4
Therefore, the brother is 4 years old.
After 4 years + 4 4
After the next 4 years + 4 4
24 is twice as old as 12; therefore for the sister to be twice as old as brother she will 24years when her brother is 12 years.
Or by calculation;
If 4 is the age for the brother, when the sister is 16, and y years will pass for the to be such that the sister is twice as old as the brother, then;
16 + y = 2(4 + y)
16 + y = 8 + 2y
16 - 8 = 2y - y
8 = y
Therefore, 8 years elapse before the sister is twice as old as the brother.
Sister will be: (16 + 8) = 24years
Brother will be: (4 + 8) = 12years
Aug 02, 2011 |
Computers & Internet