How do you get the rule of 1,3,6,10,15,21,28

Well, the sequence is basically generated by a triangle order.
You need to add a new row of dots beneath the other one every time you've completed one triangle

It's simply the triangular numbers: 1=1 1+2=3 1+2+3=6 1+2+3+4=10 and so on. You could use the formula n(n+1)/2 to determine the nth triangular number (ie the sum of the first n numbers)

Your answer would be ahere is how: perimeter is how long all the sides are. in a rectangle, there are two sets of parallel sides. so, to find this, we would to the following.(15x2)+(4x2)30+838if you have questions ask! and mark me brainliest! i really wanna level up : 3