Calculate one tenth times one and nine tenths mentally using the distributive property.
If we’re trying to multiply this in our heads, we’re breaking it up into two parts: one tenth times one and one tenth times nine tenths. One tenth times one, well anything times one is itself.
One tenth and one tenth of nine tenths we can think about it like this: what number multiplied by 10 equals nine tenths? Nine hundreds multiplied by 10 equals nine tenths. After we found both of our parts, we add them together. One tenth plus nine hundreds equals 19 hundreds, a one in the tenths place and a nine in the hundredths place.