[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
=>
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
...
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
=>
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
...
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