Multiple choice

After four years, Ruby will be five times as old as her daughter. At present, Ruby is nine times as old as her daughter. Find the present age of Ruby.

  1. 34 years

  2. 36 years

  3. 38 years

  4. 40 years
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let daughter's age be x, then Ruby's age is 9x. In 4 years, 9x + 4 = 5(x + 4). Solving this, 9x + 4 = 5x + 20, so 4x = 16, x = 4. Ruby's present age is 9 * 4 = 36.

AI explanation

Let Ruby's present age be R and her daughter's age be D. The present ratio gives R = 9D. In four years, the equation R + 4 = 5(D + 4) simplifies to R = 5D + 16. Equating the two expressions for R gives 9D = 5D + 16, so 4D = 16 and D = 4. Substituting D = 4 into the first equation gives Ruby's present age as R = 9(4) = 36 years.

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