# 7. Option 1

Diligent Masha wrote down in a row all natural numbers from 372 to 506 inclusive. Then she calculated two sums: first, the sum of all odd numbers in this row, and then the sum of all even numbers. After that, she subtracted the smaller sum from the larger one. What result did she get?
Answer: 439.

Solution. Let's divide all numbers from 372 to 506, except 506, into pairs such that each even number corresponds to the next odd number (this is possible because the last number is 505). In each pair, the odd number will be 1 greater than the even one. There will be (505 - 371) : 2 = 67 pairs in the range from 372 to 505, which means that among the numbers from 372 to 505 inclusive, the sum of the odd numbers is 67 greater. But there is still the number 506, which is even. Therefore, the sum of the even numbers is 506 - 67 = 439 greater.

## Variant 2

Diligent Masha wrote down in a row all natural numbers from 126 to 432 inclusive. Then she calculated two sums: first, of all the odd numbers in this row, and then - of all the even numbers. After that, she subtracted the smaller sum from the larger one. What result did she get?

Answer: 279.

## Variant 3

Diligent Masha wrote down in a row all natural numbers from 245 to 683 inclusive. Then she calculated two sums: first, of all the odd numbers in this row, and then - of all the even numbers. After that, she subtracted the smaller sum from the larger one. What result did she get?

Answer: 464.

## Variant 4

Diligent Masha wrote down in a row all natural numbers from 579 to 833 inclusive. Then she calculated two sums: first, of all the odd numbers in this row, and then - of all the even numbers. After that, she subtracted the smaller sum from the larger one. What result did she get?

Answer: 706.

## Variant 5

Diligent Masha wrote down in a row all natural numbers from 286 to 978 inclusive. Then she calculated two sums: first, of all the odd numbers in this row, and then - of all the even numbers. After that, she subtracted the smaller sum from the larger one. What result did she get?

Answer: 632.