Question

1）有一堆钢管,最上层3根,最下层9根,每相邻的上下两层之间相差1根,这堆钢管共有（ ）根.

Answer 1

1)(3+9)*(9-3+1)2

=(3+9)*72

=12*72

=842

=42(根)

2）假设上底是1m,下底是2m,高是3m,

S=(a+b)*h2 1*4=4 2*4=8

=（1+2）*32 S=(a+b)*h2

.=(4+8)*32

=4.5(㎡) .

=18(㎡)

3)S=(a+b)*h2

=(260-100-8)*82

.

=616(㎡)

4)S=(a+b)*h2

=(40-6-6)*62

.

=84k(d㎡)