According to the analysis, if the area occupied by pine saplings is regarded as "1", then the area occupied by cypress saplings is 80%, and the total area occupied by two saplings is (1+80%), then 9÷( 1+80%) is the area occupied by pine saplings, and then 80.

Solution: 9( 1+80%)×80%

=9÷ 1.8×0.8

=4 (hectare)

A: These two kinds of saplings each cover an area of 4 hectares.

Extended data

This topic mainly studies the associative law of multiplication and some relations between common simple multiplication.

The mathematical expression of the law of multiplicative association: a×b×c=a×(b×c).

Commonly used multiplication relations:

( 1)0。 25×4= 1。

(2)25×4= 100。

(3) 1。 25×8= 10。

(4)0。 125×8= 1。

Simple calculation of other required formulas:

(1) subtraction formula 1: a-b-c = a-(b+c).

(2) subtraction formula 2: a-b-c = a-c-b.

(3) The division formula is 1: a ÷ b ÷ c = a ÷ (b× c).

(4) division formula 2: 2:a \b \c = a \c \b b.