# If Donald is 20 and the sum of his age with his father's is 80, how many years ago was the ratio of Donald's age to his father's 1:6?

justaguide | College Teacher | (Level 2) Distinguished Educator

Posted on

Donald is 20 years old. The sum of Donald's age and his father's age is 80. This gives his father's age as 80 - 20 = 60.

If the ratio of Donald's age to his father's age was 1: 6 x years ago, we have the equation:

(20 - x) /(80 - x) = 1/6

=> 6(20 - x) = 80 - x

=> 120 - 6x = 80 - x

=> 40 = 5x

=> x = 40/5

=> x = 8

8 years ago the ratio of Donald's age to his father's age was 1: 6

agupta235 | Student, Grade 9 | (Level 1) eNoter

Posted on

Donald is 20 years old. The sum of Donald's age and his father's age is 80. Thus gives his father's age :- 80 - 20 = 60.

Let x be the no. of yrs ago,when  Donald's age to his father's age was 1: 6

If the ratio of Donald's age to his father's age was 1: 6 x years ago, we have :-

(20 - x) /(80 - x) = 1/6

=> 6(20 - x) = 80 - x

=> 120 - 6x = 80 - x

=> 40 = 5x

=> x = 40/5

=> x = 8