Join Our JEE Preparation Group
Prep with like-minded aspirants; Get access to free daily tests and study material.
Sign in
Please select an account to continue using cracku.in
↓ →
Join Our JEE Preparation Group
Prep with like-minded aspirants; Get access to free daily tests and study material.
A is a two digit positive integer. B is the two digit number obtained by reversing (inter-changing) the digits of A. If A and B are such that $$A \colon B = 4 \colon 7$$ then the number of such A is _______
Correct Answer: 4
Let $$A = 10a + b$$ and $$B = 10b + a$$ with $$a, b \ge 1$$. Then $$7(10a + b) = 4(10b + a)$$, so $$66a = 33b$$ and $$b = 2a$$. With $$b \le 9$$, $$a = 1, 2, 3, 4$$, giving $$A = 12, 24, 36, 48$$. So there are 4 such numbers.
Was this solution helpful?
Predict your JEE Main percentile, rank & performance in seconds
Educational materials for JEE preparation
Ask our AI anything
AI can make mistakes. Please verify important information.
AI can make mistakes. Please verify important information.