Eleven years ago, my brother was twice my age. In three years' time, I will be 3/4 of my brother's age. How old am I?

Question

Replys ASAP please!!! Thankyou xx

Answer 1

 

Eleven years ago, my brother was twice my age.

 

b = brother's current age

x = unknown's current age

 

b - 11 = 2(x - 11)

 

In three years' time, I will be 3/4 of my brother's age.

 

x + 3 = (3/4)(b + 3)

 

How old am I?

 

You can substitute b - 11 =2(x - 11) in for b in the second equation to solve for x.

 

Start by rewriting in terms of b.

 b - 11 = 2(x-11)

b = 2x - 22 + 11

b = 2x -11

 

x + 3 = (3/4)[(2x - 11) + 3)]

 

x + 3 = (3/4)(2x - 8)

 

4(x + 3) = 6x - 24

 

4x + 12 = 6x - 24

 

12 + 24 = 6x - 4x

 

36 = 2x 

 

 You are 18 yrs old.

 

Now check the constraints..

 

11 yrs ago

 

You currently = 18

You 11 yrs ago = 18 - 11 = 7

brother = twice your age then; 2*7 = 14

brothers current age = 14 + 11 = 25

 

In 3 yrs

You currently = 18

You 3 yrs from now = 21

Brother currently = 25

Brother 3 yrs from now = 28

 

21/28 = 3/4

 

 

Checks out.. So current ages are:

 

Your age = 18

 

Brother = 25