The sum of the even numbers is (26 + 28 + ... + 100);
The sum of the odd numbers is (25 + 27 + ... + 99)
Their difference is:
(26 + 28 + ... + 100) - (25 + 27 + ... + 99) = (26 - 25) + (28 - 27) + ... + (100 - 99)
= 1 + 1 + ... + 1
There are (100 - 26) ÷ 2 + 1 = 38 terms above which are all 1; their sum is 38 x 1 = 38.
So the difference of the sum of all even numbers and all odd numbers 25-100 is 38.
Divide the two numbers, then multiple by 100
There are 25 such numbers.
90
8
Excluding 22 and 100, there are 39
76
There are 100 even numbers between 1 and 200 (inclusive).
Divide the two numbers, then multiple by 100
There are 25 such numbers.
300.
90
8
There are 40 odd numbers between 20 and 100. Remember that an odd number is every second number. There are 80 numbers between 20 and 100, so there are 40 odd numbers and 40 even numbers.
Excluding 22 and 100, there are 39
-99
It is a sequence of numbers where the difference between successive numbers is decreasing by one.
Every second number is Even. So there are 50 even numbers from 1 to 100 if you include 100. If you do not include 100 in the count there are obviously 49. The wording of the question is not clear on whether 100 is to be included or not.