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What is the value of aligned & 2(2 1)+3(3 2 1)+4(4 3 2 1)+ & 5(5 4 3 2 1)+ + & 9(9 8 7 6 5 4 3 2 1)+2 ? aligned

Options

  1. A11 !
  2. B10 !
  3. C10+10 !
  4. D11+10 !

Correct answer

B. 10 !

Step-by-step solution

aligned & 2(2 1)+3(3 2 1)+4(4 3 2 1)+5 & (5 4 3 2 1)+ . .+9(9 8 7 6 5 4 3 & 2 1)+2 & =2+2.2!+3.3!+4.4!+5.5!+ .+9.9! & =2!+(2+1)+3.3!+4.4!+5.5!+ .+9.9! & =3!+3.3!+4.4!+5.5!+ .+9.9! aligned Proceed further we get =9!+9.9!=10!

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