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How many hectares does pine and cypress cover?
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.