Question

Sum of all 2 digit positive nums

Answer 1

Answer: I tried....

To find the sum of all two-digit positive numbers, you can use a mathematical formula for the sum of an arithmetic series. In this case, you want to find the sum of all two-digit numbers from 10 to 99.

The formula for the sum of an arithmetic series is:

Sum = (n/2) * [2a + (n-1)d]

Where:

n is the number of terms.

a is the first term.

d is the common difference between terms.

For this case:

n = There are 90 two-digit numbers (from 10 to 99), so n = 90.

a = 10 (the first two-digit number).

d = 1 (since the difference between each consecutive two-digit number is 1).

Now, plug these values into the formula:

Sum = (90/2) * [2 * 10 + (90-1) * 1]

Sum = (45) * [20 + 89]

Sum = 45 * 109

Sum = 4,905

So, the sum of all two-digit positive numbers from 10 to 99 is 4,905.

Answer 2

The sum of all two-digit positive numbers is 4905.

Explanation:

In order to find the sum of all two-digit positive numbers, we can use the arithmetic sum formula for the sum of an arithmetic sequence:

`\sf S = (n)/(2) \cdot (a + l)`

Where:

• S is the sum of the sequence.
• n is the number of terms in the sequence.
• a is the first term.
• l is the last term.

In this case, the first two-digit positive number is: a = 10(the smallest two-digit number) and the last two-digit positive number is l = 99 (the largest two-digit number).

The number of terms n is 99 - 10 + 1 = 90.

Plugging these values into the formula:

`\sf S = (90)/(2) \cdot (10 + 99) = 45 \cdot 109 = \boxed{\sf 4905}`

So, the sum of all two-digit positive numbers is 4905.