Question 570812
The ratio of their ages should decrease with time, but you could not calculate the answer ratio without more information.
Depending on what class you are in, you would justify that the ratio decreases in a different way, but for a multiple choice problem, you would not need to prove it.
The ratios shown, calculated by dividing (rounding if needed) are:
{{{5/4}}}=1.25
{{{11/8}}}=1.375
{{{9/7}}}=1.286 (rounded)
{{{15/13}}}=1.154 (rounded)
{{{19/15}}}=1.267 (rounded)
The only answer choice that is less than {{{5/4=1.25}}} is 15:13
If you are curious (and want to know if it makes sense), making the current age of the wife {{{x}}}, the current age of the husband would be {{{1.25x}}}, so after 20 year the ratio would be
{{{(1.25x+20)/(x+20)=15/13}}} --> {{{13(1.25x+20)=15x+20)}}} --> {{{16.25x+260=15x+300}}} --> {{{1.25x=40}}} --> {{{x=32}}}
That would make the wife 32 years old and the husband {{{1.25*35=40}}} at the time. It is likely that they would both be alive 20 years later and would be 52 and 60, and the ratio of their ages then would be
{{{60/52=15/13}}}