Decimals with tenths (one decimal digit) plus how to add them with mental math - 4th grade math

The first digit after the decimal point tells us the number of tenths (the tenths place). We convert between fractions and decimals, practicing this simple concept -- an introduction to decimals.

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In this second part of the lesson, I show how to add decimals with one decimal digit (tenths), such as 0.2 + 0.9 or 3.7 + 0.7, using mental math. Note that 0.2 + 0.9 is NOT 0.11! Lastly we also convert between centimeters and millimeters. This is a nice application of the concept just learned, since one millimeter is a tenth of a decimeter.

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See also

Mixed numbers to fractions and vice versa — video lesson

Math Mammoth Grade 4 curriculum

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