Q81.A person forgets his 4-digit ATM pin code. But he remembers that in the code all the digits are different, the greatest digit is 7 and the sum of the first two digits is equal to the sum of the last two digits. Then the maximum number of trials necessary to obtain the correct code is________.
What This Question Tests
This is a challenging counting problem that requires careful casework. It tests the ability to enumerate possibilities based on multiple constraints: distinct digits, a fixed greatest digit, and a specific sum relationship between pairs of digits.
Concepts Tested
Formulas Used
Permutations P(n, r) = n! / (n-r)!
๐ NCERT Sections This Tests
1.28 โ Calculate The Mass Percentage Of Aspirin (C9H8O4) In Acetonitrile (Ch3Cn) When
Chemistry Class 11 ยท Chapter 1
1.28 Calculate the mass percentage of aspirin (C9H8O4) in acetonitrile (CH3CN) when 6.5 g of C9H8O4 is dissolved in 450 g of CH3CN.
5.12 โ Write All The Geometrical Isomers Of [Pt(Nh3)(Br)(Cl)(Py)] And How Many Of
Chemistry Class 11 ยท Chapter 5
5.12 Write all the geometrical isomers of [Pt(NH3)(Br)(Cl)(py)] and how many of these will exhibit optical isomers?
8.17 โ Complete Each Synthesis By Giving Missing Starting Material, Reagent Or Products
Chemistry Class 12 ยท Chapter 8
8.17 Complete each synthesis by giving missing starting material, reagent or products
๐ Question Details
- Chapter
- Permutation & Combination
- Topic
- Counting principles and permutations
- Year
- 2023
- Shift
- 15 Apr Shift 1
- Q Number
- Q81
- Type
- Numerical
- NCERT Ref
- Class 11 Mathematics Ch 7: Permutation & Combination
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