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The sum of the digits in the unit place of all numbers formed with the help of 3,4,5,6 taken all at a time isA. 432B. 108C. 36D. 18 |
Answer» Correct Answer - B If we fixed 3 at units place. Total possible number is `3"!"` i.e., 6. Sum of the digits in unit place of all these numbers `=3"!" xx 3` Similarly, if we fixed 4, 5 and 6 at units place, in each case total possible numbers are `3"!"`. Required sum of unit digits of all such numbers `= (3 + 4+ 5 + 6) xx 3"!"` `= 18 xx 3"!" = 18 xx 6 = 108` |
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