Question
How many four-letter words without repetition having
exactly two vowels can be formed by using the letters of the word "CAMPFIRE"?Solution
"CAMPFIRE" has 5 consonants and 3 vowels.
Number of ways to select the letters = 3C2 × 5C2 = 3 × 10 = 30
Arrangements of 4 letters = 4! = 24
Total number of words formed = 30 × 24 = 720
What will come in place of the question mark (?) in the following series?
21, 36, 66, 126, ?, 486
10,14,26,42,70,?
81, 41, 42, 64.5, ?, 330
What will come in place of the question mark (?) in the following series?
5, 14, 41, 122, 365, 1094, ?
1500 Â Â Â 150Â Â Â 30Â Â Â ? Â Â Â Â 3.6Â Â Â Â 1.8
Find the missing number in the series:
7, 21, 19, 57, 55, ?
71, 79, 88, 152, ?, 393
1     1      4       ?      280       3640
...3, 10, 29, 66, ?
Find the missing number in the given number series.
 1165, ?, 1040, 985, 935, 890Â
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