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If n cr–1 = 56, ncr = 28 and n cr 1 = 8, then r is equal to (a) 8 (b) 6 (c) 5 (d) none of these?
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If n cr–1 = 56, ncr = 28 and n cr 1 = 8, then r is equal to (a) 8 (b) ...
Solution:
Given, ncr-1 = 56, ncr = 28 and ncr1 = 8
We know that ncr = ncr-1 × (n – r + 1)/r
On substituting the given values, we get
28 = 56 × (n – r + 1)/r
1/2 = (n – r + 1)/r
r/2 = n – r + 1
n = 3r/2 – 1
Also, ncr-1 = ncr × (r)/(n – r + 1)
On substituting the given values, we get
56 = 28 × (r)/(n – r + 1)
n – r + 1 = 2r
n = 3r – 1
On solving the above two equations, we get
3r/2 – 1 = 3r – 1
3r = 4r – 2
r = 2
Therefore, option (d) none of these is the correct answer as r is not equal to any of the given options.
HTML Code:
Given, ncr-1 = 56, ncr = 28 and ncr1 = 8
We know that ncr = ncr-1 × (n – r + 1)/r
On substituting the given values, we get
28 = 56 × (n – r + 1)/r
1/2 = (n – r + 1)/r
r/2 = n – r + 1
n = 3r/2 – 1
Also, ncr-1 = ncr × (r)/(n – r + 1)
On substituting the given values, we get
56 = 28 × (r)/(n – r + 1)
n – r + 1 = 2r
n = 3r – 1
On solving the above two equations, we get
3r/2 – 1 = 3r – 1
3r = 4r – 2
r = 2
Therefore, option (d) none of these is the correct answer as r is not equal to any of the given options.
HTML Code:
Solution:
Given, ncr-1 = 56, ncr = 28 and ncr1 = 8
We know that ncr = ncr-1 × (n – r + 1)/r
On substituting the given values, we get
28 = 56 × (n – r + 1)/r
1/2 = (n – r + 1)/r
r/2 = n – r + 1
n = 3r/2 – 1
Also, ncr-1 = ncr × (r)/(n – r + 1)
On substituting the given values, we get
56 = 28 × (r)/(n – r + 1)
n – r + 1 = 2r
n = 3r – 1
On solving the above two equations, we get
3r/2 – 1 = 3r – 1
3r = 4r – 2
r = 2
Therefore, option (d) none of these is the correct answer as r is not equal to any of the given options.
Community Answer
If n cr–1 = 56, ncr = 28 and n cr 1 = 8, then r is equal to (a) 8 (b) ...
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If n cr–1 = 56, ncr = 28 and n cr 1 = 8, then r is equal to (a) 8 (b) 6 (c) 5 (d) none of these?
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If n cr–1 = 56, ncr = 28 and n cr 1 = 8, then r is equal to (a) 8 (b) 6 (c) 5 (d) none of these? for CA Foundation 2024 is part of CA Foundation preparation. The Question and answers have been prepared according to the CA Foundation exam syllabus. Information about If n cr–1 = 56, ncr = 28 and n cr 1 = 8, then r is equal to (a) 8 (b) 6 (c) 5 (d) none of these? covers all topics & solutions for CA Foundation 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for If n cr–1 = 56, ncr = 28 and n cr 1 = 8, then r is equal to (a) 8 (b) 6 (c) 5 (d) none of these?.
If n cr–1 = 56, ncr = 28 and n cr 1 = 8, then r is equal to (a) 8 (b) 6 (c) 5 (d) none of these? for CA Foundation 2024 is part of CA Foundation preparation. The Question and answers have been prepared according to the CA Foundation exam syllabus. Information about If n cr–1 = 56, ncr = 28 and n cr 1 = 8, then r is equal to (a) 8 (b) 6 (c) 5 (d) none of these? covers all topics & solutions for CA Foundation 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for If n cr–1 = 56, ncr = 28 and n cr 1 = 8, then r is equal to (a) 8 (b) 6 (c) 5 (d) none of these?.
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