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akijuneja
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A person was dialing a telephone. He forgot the last three 26 Jun 2013, 03:21
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55% (hard)

Question Stats:

63% (02:23) correct 37% (02:47) wrong based on 196 sessions

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A person was dialing a telephone. He forgot the last three digits of the six-digit telephone number but rembered that the number formed by the last three digits in the same order was a perfect square. What is the probability he dialed a right number?

(A) 1/32
(B) 1/46
(C) 1/49
(D) 1/36
(E) 1/18


Please explain.
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A
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Bunuel
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A person was dialing a telephone. He forgot the last three 26 Jun 2013, 03:33
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akijuneja
A person was dialing a telephone. He forgot the last three digits of the six-digit telephone number but rembered that the number formed by the last three digits in the same order was a perfect square. What is the probability he dialed a right number?

(A) 1/32
(B) 1/46
(C) 1/49
(D) 1/36
(E) 1/18


Please explain.
Show more

There are following perfect squares less than 1,000:
000 (0^2);
001 (1^1);
004;
009;
016;
025;
036;
049;
064;
081;
100;
121;
144;
...
961 (31^2).

Total of 32 perfect squares.

The probability = 1/32.

Answer: A.
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A person was dialing a telephone. He forgot the last three 20 Apr 2014, 08:13
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Bunuel
akijuneja
A person was dialing a telephone. He forgot the last three digits of the six-digit telephone number but rembered that the number formed by the last three digits in the same order was a perfect square. What is the probability he dialed a right number?

(A) 1/32
(B) 1/46
(C) 1/49
(D) 1/36
(E) 1/18


Please explain.

There are following perfect squares less than 1,000:
000 (0^2);
001 (1^1);
004;
009;
016;
025;
036;
049;
064;
081;
100;
121;
144;
...
961 (31^2).

Total of 32 perfect squares.

The probability = 1/32.

Answer: A.
Show more

@Bunuel:
I got the favorable outcome as 32, but I was lost after that.
Probability = Favorable outcome/Total Outcome. Total outcome I took in this case as 900(9*10*10). Can you please help what exactly I am doing wrong here.
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A person was dialing a telephone. He forgot the last three 20 Apr 2014, 11:49
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Bunuel
akijuneja
A person was dialing a telephone. He forgot the last three digits of the six-digit telephone number but rembered that the number formed by the last three digits in the same order was a perfect square. What is the probability he dialed a right number?

(A) 1/32
(B) 1/46
(C) 1/49
(D) 1/36
(E) 1/18


Please explain.

There are following perfect squares less than 1,000:
000 (0^2);
001 (1^1);
004;
009;
016;
025;
036;
049;
064;
081;
100;
121;
144;
...
961 (31^2).

Total of 32 perfect squares.

The probability = 1/32.

Answer: A.

@Bunuel:
I got the favorable outcome as 32, but I was lost after that.
Probability = Favorable outcome/Total Outcome. Total outcome I took in this case as 900(9*10*10). Can you please help what exactly I am doing wrong here.
Show more

A person new that the number formed by the last three digits was a perfect square. We found that those three digits can take 32 values, so 32 is the total. Only 1 out of these 32 is a correct number, so 1 is favorable. Hence probability 1/32.

Does this make sense?
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A person was dialing a telephone. He forgot the last three 11 Dec 2022, 07:17
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Given: A person was dialing a telephone. He forgot the last three digits of the six-digit telephone number but remembered that the number formed by the last three digits in the same order was a perfect square.

Asked: What is the probability he dialed a right number?

There are 32 3-digit square number = {000,001,004,.....,961}
The probability he dialed a right number = 1/32

IMO A
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A person was dialing a telephone. He forgot the last three 15 Jun 2024, 11:53
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