Standard deviation is: It is a measure of how spread out numbers are. It is the square root of the Variance, and the Variance is the average of the squared differences from the Mean.
For example: To find the standard deviation, you have to add up all the numbers in the data set, then divide by how many numbers there are, and that will get you your answer.
Example, Say your data set is: 9, 2, 5, 4, 12, 7, 8, 11, 9, 3, 7, 4, 12, 5, 4, 10, 9, 6, 9, 4.
The Mean is: 9 + 2 + 5 + 4 + 12 + 7 + 8 + 11 + 9 + 3 + 7 + 4 + 12 + 5 + 4 + 10+ 9 + 6 + 9 + 4. Over 20. That equals: 104 over 20 = 7.
So, the Standard Variance and Mean is: 7 for this problem.
There are infinitely many triangles that can be constructed. The three angles can be fixed but the side lengths can scale up or down (larger or smaller). For example, say we had a triangle with sides of 3,4,5. A similar triangle to this would be 6,8,10. The two similar triangles have the same corresponding angles (which are congruent to one another). That example shows how it's possible to make infinitely many triangles based on scaling an original triangle.
In short, there is no limit to how many triangles you can make as long as the angles stay the same.