Select the correct answerEighteen years ago, the ratio of A’s age to B’s age was 8 : 13. Their present ratios are 5 : 7. What is the present age of A ?Options60 years50 years40 years70 years
Question
Select the correct answerEighteen years ago, the ratio of A’s age to B’s age was 8 : 13. Their present ratios are 5 : 7. What is the present age of A ?Options60 years50 years40 years70 years
Solution
To solve this problem, we need to use the concept of ratios and simple algebra. Here are the steps:
Step 1: Let's denote the present ages of A and B as A and B respectively. According to the problem, 18 years ago, the ratio of A's age to B's age was 8:13. So, we can write this as:
(A - 18) / (B - 18) = 8 / 13
Step 2: The problem also states that their present ages are in the ratio 5:7. So, we can write this as:
A / B = 5 / 7
Step 3: Now we have a system of two equations. We can solve this system by substitution or elimination method. Let's multiply the second equation by B to isolate A:
A = 5B / 7
Step 4: Substitute A from the second equation into the first equation:
(5B / 7 - 18) / (B - 18) = 8 / 13
Step 5: Solve this equation for B. After solving, you will get B = 70.
Step 6: Substitute B = 70 into the equation A = 5B / 7 to find A. After substituting, you will get A = 50.
So, the present age of A is 50 years. Therefore, the correct answer is 50 years.
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