Answer:
John will be 16 years old when he is twice as old as his brother, which will then be 8.
Step-by-step explanation:
Currently John is 12, and is three times as old as his brother thus, his brother is 12 divided by 3, which is 4 years old.
Thus when John is 12, his brother is 4. There is thus a 8 year difference between the two brothers.
So we can write a small equation to solve John’s age when he will be twice as old.
John’s age = X
John’s Brothers age = X - 8
Thus : X - 8 = X/2, John’s age minus the difference of 8 years must equal John’s age divided by 2, to make John twice as old as his brother.
X - 8 = x/2
X = X/2 + 8
(2*X)/2 = (X/2) + (16/2) - Place all numbers as fractions of 2 by multiplying x 2
2*X = X + 16
2*X -X = 16
X+X -X = 16
X = 16
John’s age will be 16 when he is twice as old as his brother which will be 8.
John : 16 - 12 = 4 : Subtract current Age
His Brother: 8 - 4 = 4 : Subtract current Age
In 4 years time John will be twice as old as his brother
16 = 8 * 2
