Four-digit perfect squares with repeated digits
CAT 2007 Slot 1 · Quantitative Ability · Medium · Number System
This is a medium Quantitative Ability question from the CAT 2007 Slot 1 paper. It tests Number System. The full answer key and a step-by-step explanation are below — try it yourself first, then reveal the solution.
Consider four-digit numbers for which the first two digits are equal and the last two digits are also equal. How many such numbers are perfect squares?
- A.
3
- B.
2
- C.
4
- D.
0
- E.
1
Answer
E
Explanation
The number is . For to be a square, must be divisible by 11 is divisible by 11. Testing pairs with : is the only valid number.
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