A) 3000
B) 3050
C) 4050
D) None of these
Correct Answer: B
Solution :
The sum of integers from 1 to 100 that are divisible by 2 or 5 = sum of series divisible by 2 + sum of series divisible by 5 - sum of series divisible by 2 and 5. \[=(2+4+6+......+100)+(5+10+15.......+100)\] \[-(10+20+30+........+100)\] \[=\frac{50}{2}\left\{ 2\times 2+(50-1)2 \right\}+\frac{20}{2}\left\{ 2\times 5+(20-1)5 \right\}\] \[-\frac{10}{2}\left\{ 10\times 2+(10-1)10 \right\}\] \[=2550+1050-550=3050\].
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