The perimeter of the square to the right is 40cm what is the length of the diagonal

the question does not present the picture, but this does not interfere with the resolution

we know that

perimeter square=4*b

where

b is the length side of the square

perimeter=40 cm

so

4*b=40

b=40/4

b=10 cm

Find the diagonal applying the Pythagoras Theorem

D²=b²+b²> D²=10²+10²> D²=200> D=√200

D=10√2 cm

the answer is

you need a common difference between consecutive terms to be constant, like 1,2,3,4 or 2,4,6,8, or 1,3,6,9