When multiplyingreal numbers, the product will be positive if the signs are the same, and it will be negative if the signs are different.
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Same Sign & Different Signs
(+)(+)=(+) & (+)(-)=(-)
(-)(-)=(+) & (-)(+)=(-)
In our case both numbers are positive, so the product will be positive.
We can also solve this problem using our mental math skills. We are going to use the Distributive Property. Notice that we can rewrite 4.1 as a sum of an integer and a decimal.
4.1 = 4+0.1 ⇔ 5 * 4.1 = 5( 4+0.1)
We can now calculate the product using the Distributive Property.
5(4+0.1) = 5*4+5*0.1 = 20+0.5
We got the same final solution, 20.5.
