Is there a formula for finding the total number of math kindergarten questions?
From top to bottom, from the first floor to the bottom floor:1+2+3+4+5+6+7 = (1+7) × 7/2 = 28.
Note: the sum of the head and tail is equal to 8, and the sum of the second number and the penultimate number is also equal to 8. This combination has 7/2 groups, so it is 8×7/2=28.
Summary: generally, it is 1+2+3+4+...+n( 1 plus n)=( 1+n)×n/2.