1. The probability that atleast one of them is even is 1-(probability that none of them are even)
1-1/4= 3/4
3. I think the answer is D.
4. The answer is 13. The sequence repeats itself after 6 numbers.
-5,4,9,5,-4,-9,-5,4,9,5,-4,-9.
The sum of the first six terms is 0. 96 is the last multiple of 6 less than 100 therefore the sum of the first 96 terms is 0. The sum of the next
4 terms i.e 97,98,99,100 is
-5+4+9+5 = 13