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in Mathematics by (71.2k points)

The value of 47C4 + 5j =1 52–jC3 is equal to_____ 

(a) 47C5 

(b) 52C5 

(c) 52C

(d) 53C7

1 Answer

+1 vote
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Best answer

Correct option: (c) 52C4

Explanation:

47C4 + 5j=1 52–jC3 

= 47C4 + 51C3 + 50C3 + 49C3 + 48C3 +  47C3   (1)

using nCr + nCr–1 = n+1Cr we get 47C4 + 47C3 = 48C4

∴ from (1) expression is 51C3 + 50C3 + 49C3 + 48C3 + 48C4 

= 51C3 + 50C3 + 49C3 + 49C4 

= 51C3 + 50C3 + 50C4 

= 51C3 + 51C4 

= 52C4

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