answer

the sum of the integers from1to100 which are divisible by 2 or 5
(1)3000
(2)3010
(3)3150
(4)3050

1 Answers

sum of integers divisible by

2!= 2+4+6+...100 = 50.51 = 2550

5.. = 5+10+15+... 100 = 20.105/2 = 1050

10.. = 10+20+30+... + 100 = 110.10/2 = 550

No divisible by 2 or 5 = 2550+1050-550

last step is tricky but comes from venn diagram!

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