,900, 120000,90

Second, (1)36=2.

×2×3×3

78=2×3× 13

90=3×3×2×5

(2) Maximum common factor 8

Least common multiple 504;

Maximum common factor 1

Minimum common multiple 72;

(84,56) = 28

The longest side is 28 meters.

56/28×(84/28)=6 (block)

Four. = ( 1+ 1/2+ 1/3+ 1/4) × ( 1/2+ 1/3)+( 1/4) 2+ 1/3+ 1/4)×( 1/2+ 1/3+ / kloc-0//4)- 1/5×( 1/2+ 1/3+ 1/4)

= 1/5