[GMAT math practice question]
Alice makes 2-digit codes using the 26 letters of the alphabet. Letters may be used repeatedly, and at least one vowel must be used. How many possible codes can she make?
A. 235
B. 256
C. 360
D. 625
E. 676
Alice makes 2-digit codes using the 26 letters of the alphab
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- Max@Math Revolution
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The number of vowels is 5 (a,e,i,o,u). So, the number of codes is equal to the number of 2-digit codes with no restrictions minus the number of codes that contain no vowels. This is given by
26*26 - 21*21 = (26 + 21)(26 - 21) = 47*5 = 235.
Therefore, the answer is A.
Answer: A
The number of vowels is 5 (a,e,i,o,u). So, the number of codes is equal to the number of 2-digit codes with no restrictions minus the number of codes that contain no vowels. This is given by
26*26 - 21*21 = (26 + 21)(26 - 21) = 47*5 = 235.
Therefore, the answer is A.
Answer: A
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Each code must have at least one vowel. Thus, we have 3 cases for creating the codes: 1) vowel-consonant, 2) consonant-vowel, and 3) vowel-vowel.Max@Math Revolution wrote:[GMAT math practice question]
Alice makes 2-digit codes using the 26 letters of the alphabet. Letters may be used repeatedly, and at least one vowel must be used. How many possible codes can she make?
A. 235
B. 256
C. 360
D. 625
E. 676
Case 1: vowel-consonant
We have 5 x 21 = 105 possible codes.
Case 2: consonant-vowel
We also have 21 x 5 = 105 possible codes.
Case 3: vowel-vowel
We have 5 x 5 = 25 possible codes.
Thus, the total number of possible codes is 105 + 105 + 25 = 235.
Answer: A
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