CA Foundation doubt
How do I solve factorial sums like 1/7! + 1/8! = N/9! in Permutations and Combinations?
Can anyone explain how to solve this sum of p&c ch ?
Asked by Krupa··2 answers
2 replies
BrunoAI answerAI first answer — verify with your teacher
Trick: multiply both sides by the biggest factorial, then cancel. Q7: 1/7! + 1/8! = N/9! Multiply by 9!: - 9!/7! = 9 x 8 = 72 - 9!/8! = 9 N = 72 + 9 = 81, so option (a). Q8: 1/9! + 1/10! = x/11! Multiply by 11!: - 11!/9! = 11 x 10 = 110 - 11!/10! = 11 x = 110 + 11 = 121. That is not in the options, so (d) None of these. Key idea: n! = n x (n-1)!, so 9!/7! = 9 x 8.
Krupa
Thank you Bruno
Related questions
What is the value of 0! in Permutations and Combinations?
0! is defined as 1. This keeps formulas like nPr and nCr valid when r = n or r = 0.
How do you simplify n!/(n-2)!?
Write n! as n x (n-1) x (n-2)!, then cancel (n-2)!. The result is n(n-1).
Is factorial defined for negative numbers?
No. In the CA Foundation syllabus, factorial is defined only for non-negative integers.
Have a doubt like this, or know the answer?
Ask and reply in the free Studycaller app. Students and Bruno answer fast.
Related doubts
CA FoundationBusiness Laws - answering case study questions
How do I understand case law questions and write answers for 2, 4 or 5 marks in CA Foundation Business Laws?
BrunoAI answer
Case law questions get easy once you follow a fixed 4-step format (ICAI marks mostly go for the provision + correct conclusion): 1. Provision: state the relevant law in 2-3 lines, with the section only if you're sure (e.g. "As per Section 10 of the Indian Contract Act, 1872..."). 2. Facts: one line linking the case facts to that provision. 3. Analysis: apply the law to the facts and explain why it fits or fails. 4. Conclusion: a clear yes/no answer to exactly what is asked. For 2 marks keep each step to a line; for 4-5 marks expand the provision and analysis, and answer each sub-part separately. To understand them better, read the provision first, then solve the cases in notes [2] and [4] and compare your answer with the given solution.
Read full answer →
1 answer 15 Nov 2026
CA FoundationInventories - valuation under AS 2
Can anyone teach me the Inventories chapter or share notes that can help?
Devendra
Sure ,hey if you want you can also prefer CA Hardik manchanda sir's video on yt it will help you a lot 😊
Read full answer →
2 answers 15 Nov 2026
CA FoundationAS 3 Cash Flow Statement - interest and dividend classification
Why are cash flows of a financial entity treated differently from those of a non-financial entity?
Veer
Dono ke cash flow treatment me farq isliye hai kyunki dono ka main business (core operation) alag hota hai. • Non-Financial Entity: Inka main kaam goods/services bechna hai, isliye loan aur interest inke liye Investing/Financing hai. • Financial Entity (Banks): Inka main kaam hi paisa lena-dena hai, isliye interest aur loans inke liye Operating hai.
Read full answer →
2 answers 15 Nov 2026
CA FoundationCA Foundation Quantitative Aptitude - MCQ practice material
Does anyone have the latest MCQ bank for Quantitative Aptitude for CA Foundation?
Chandan
Behen tum notes wale option par search karlo, scanner ke liye
Read full answer →
3 answers 14 Nov 2026
CA FoundationQA Statistics - MCQ practice material
Is there a latest and helpful PDF for CA Foundation QA Statistics MCQ practice in this app?
1 answer 14 Nov 2026
CA FoundationAnswer writing for case law questions in Business Laws
How should I write answers to case law questions in CA Foundation Business Laws?
Vala
Search on ytt
Read full answer →
7 answers 14 Nov 2026
Free app · 5 lakh+ learners
Ask your doubt in the Studycaller app
Read full notes, ask doubts, follow toppers and track your study hours — free on Android and iPhone.