Question

Please help as soon as possible!!

Answer 1

Explanation:

`P_1=3=2+1=(2*(2+1))/(2) \\\\P_2=6=3+2+1=(3*(3+1))/(2) \\\\P_3=4+3+2+1=(4*(4+1))/(2)=(4*5)/(2) =10\\\\P_4=5+4+3+2+1=(5*(5+1))/(2)=(5*6)/(2) =15\\\\...\\P_(n)=(n+1)+n+(n-1)+(n-2)+...+2+1\\\\=((n+1)*((n+1)+1))/(2)\\\\=((n+1)*(n+2))/(2)\\\\\\P_5=(6*7)/(2)=21\\`

a) There are 12 cubes left, so we need 21-12=9 wood cubes.

b)

`P_(10)=(11*12)/(2)=66\\\\`