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Best answer
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Let five digit A, B, C, D, E then A + B + C + D + E = 7

given n = 7, r = 5 we know that

n + r – 1 C  r - 1  = 7+5 -1 C 5-1 = 11 C 4 = 11x 10x9x8/1x2x3x4 =330

Answer B

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This simple star-bar problem with IODB template where the a+b+c+d+e=7 which is equivalent to Combination with repitition, where content does not matters only order matters.

 

THere are 7 stars and 4 bars. (7+4)C4==330
Answer:

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