Is the sum of 1 and 101 odd or even?

Is the sum of 1 and 101 odd or even?

Using the formula of arithmetic sequence, we can get: (1 + 101) x 101 / 2 = 5151
So it's odd

Is the sum of 1 + 2 + 3 +. + 101 odd or even? Why?

You can calculate the value and use the formula of summation of arithmetic sequence
The sum of the first and last terms multiplied by the number of terms divided by two
That is, (1 + 101) × 101 △ 2 = 5151, so it is odd

The two odd numbers adjacent to 4 are______ The two even numbers adjacent to 4 are______ ．

The two odd numbers adjacent to 4 are 3 and 5, and the two even numbers adjacent to 4 are 2 and 6