Question

Помогите пожалуйста, решите удобным способом 2 примера. 1. 1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20 2. 2+4+6+8+10+12+14+16+18+20

Answer 1

1. (1+19)+(2+18)+(3+17)+(4+16)+(5+15)+(6+14)+(7+13)+(8+12)+(9+11)+(10+20)=20+20+20+20+20+20+20+20+20+30=210.

2. (2+18)+(4+16)+(6+14)+(8+12)+(10+20) =20+20+20+20+30=110.

Если сложить более удобным способом, приводя к круглым числам и сложить между собой.

Answer 2

Сложить единицы и десятки отдельно,а потом сложить вместе
получится
1:45+206=251
2:22+90=112

Answer 3

Solution:

To solve the given examples, we can use basic arithmetic operations. Let's calculate the results for each example:

1. 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 11 + 12 + 13 + 14 + 15 + 16 + 17 + 18 + 19 + 20:

To find the sum of consecutive numbers from 1 to 20, we can use the formula for the sum of an arithmetic series:

Sum = (n/2)(first term + last term)

In this case, the first term is 1, the last term is 20, and the number of terms (n) is 20.

Sum = (20/2)(1 + 20) = 10(21) = 210

Therefore, the sum of the numbers from 1 to 20 is 210.

2. 2 + 4 + 6 + 8 + 10 + 12 + 14 + 16 + 18 + 20:

To find the sum of even numbers from 2 to 20, we can use the formula for the sum of an arithmetic series.

In this case, the first term is 2, the last term is 20, and the common difference is 2 (since we are adding even numbers).

Sum = (n/2)(first term + last term)

The number of terms (n) can be calculated by dividing the difference between the last term and the first term by the common difference and adding 1.

n = (20 - 2)/2 + 1 = 10

Sum = (10/2)(2 + 20) = 5(22) = 110

Therefore, the sum of the even numbers from 2 to 20 is 110.

I hope this helps! Let me know if you have any further questions.