Question 1182774

Harry is 3 times as old as Louise was when Harry was as old as Louise is now. When Louise is as old as Harry is now, they will be 28 together. How old is Harry and Louise now?
<pre>That woman ABSOLUTELY has no clue. Thus, her answer is SHEER RUBBISH, so don't even look at her setup and solution.

Let Harry's and Louise's ages be H and L, respectively
It's absolutely essential to determine who's older. From the reading, it's obvious that Harry is older.

With Harry being older the difference in their ages is H - L
So, H - L years ago, Harry was L years-old
And, H - L years ago, Louise was L - (H - L), or 2L - H years-old
Given that Harry is 3 times as old as Louise was when Harry was as old as Louise is now, we get:
H = 3(2L - H)
H = 6L - 3H
4H = 6L___2H = 3L ----- eq (i)

When Louise is as old as Harry is now, Louise will be H years-old
And, at that time, Harry will be H + H - L = 2H - L
Given that, when Louise is as old as Harry is now, their ages will sum to 28, we have:
H + 2H - L = 28
3H - L = 28
3H - 28 = L ----- eq (ii)

2H = 3(3H - 28) ------ Substituting 3H - 28 for L in eq (i)
2H = 9H - 84
2H - 9H = - 84
- 7H = - 84
Harry's age, or {{{highlight_green(matrix(1,5, H, "=", (- 84)/(- 7), "=", 12))}}}

2(12) = 3L ------ Substituting 12 for H in eq (i)
Louise, or {{{highlight_green(matrix(1,6, L, "is", 2(12)/3, "=", 8, years-old))}}}</pre>