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`7^(103)` when divided by 25 leaves the remainder .A. 20B. 16C. 18D. 15 |
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Answer» Correct Answer - c We have, ` 7^(103) = 7(49)^(51)` `rArr 7^(103) = 7(50 -1)^(51)` ` rArr 7^(103) = 7{""^(51)C_(90)(50)^(51) - ""^(51)C_(r)(50)^(50) + ""^(51)C_(2)(50)^(49)...-1}` ` rArr 7^(103) = 7{(50)^(51) - ""^(51)C_(1)(50)^(50) + ""^(51)C_(2)(50)^(49)...}-7` `rArr 7^(103) = 7{(50)^(51) - ""^(51)C_(1)(50)^(50) + ""^(51)C_(2)(50)^(49)...}-7 - 18 + 18` `rArr 7^(103) = 7{(50)^(51) - ""^(51)C_(1)(50)^(50) + ""^(51)C_(2)(50)^(49)...}-25 + 18` `rArr 7^(103)` = Multiple of 25 + 18 Hence, remainder = 18. |
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