Subject
Quantitative Aptitude
Topic
Permutation & Combination
Rohan decided to make collections of numbers greater than 0 and less than a million with the digits 0, 7 and 8. How many numbers are possible?
Rohan decided to make collections of numbers greater than 0 and less than a million with the digits 0, 7 and 8. How many numbers are possible?
ক)
1086খ)
486গ)
728ঘ)
1000ঙ)
None of the aboveExplanation
A million is 1000000(first seven digit’s number). So, we need to find how many numbers of less than 7 digits can be formed using the digits 0, 7 and 8. This can be done as there are 2 possibilities at this first digit ⇒ 7 and 8 At all other places, any of the three numbers can be present. So there are three possibilities for all other digit’s places, therefore possible numbers Number of 1 digit numbers = 2 Number of 2 digit numbers = 2 × 3 = 6 Number of 3 digit numbers = 2 × 3 × 3 = 18 Number of 4 digit numbers = 2 × 3 × 3 × 3 = 54 Number of 5 digit numbers = 2 × 3 × 3 × 3 × 3 = 162 Number of 6 digit numbers = 2 × 3 × 3 × 3 × 3 × 3 = 486 Total number of such numbers = 2 + 6 + 18 + 54 + 162 + 486 = 728Related questions
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