Answer
$390$
Work Step by Step
We start with the given expression: $25\times3.9\times4$
The commutative property of multiplication states that changing the order of the factors does not affect the product.
We use this property to rearrange the factors: $25\times4\times3.9$
We simplify using the order of operations:
We multiply from left to right: $100\times3.9=390$