15 years hence, A will be twice as old as B, but five years ago A was
4 times as old as B. Find the difference of their present ages.
Answers
Step-by-step explanation:
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Given - Age comparison 15 years ago and five years ago
Find - Difference of present ages
Solution - The difference in present ages is 30 years.
Let the age of A be x and the age of b be y years old. Now, 15 years later, their ages will be related as follows.
x + 15 = 2(y + 15)
Solving this we get -
x + 15 = 2y + 30
x - 2y = 15
Let this be equation 1.
Now, 5 years ago, their ages were as follows.
x - 5 = 4(y - 5)
x - 5 = 4y - 20
x - 4y = - 15
Let this be equation 2.
Solving the equation 1 and 2 for the value of y.
x - 2y = 15
x - 4y = - 15
On adding the two equations, we get, 2y = 30
y = 15
Finding the age of A-
x - 2(15) = 15
x - 30 = 15
x = 15 + 30
x = 45
So, the age of A is 45 years and the age of B is 15 years.
The difference between the present age = 45 - 15
Difference between the present age = 30 years.
Difference between their present ages is 30 years.