Adding and subtracting decimals is the almost the same as adding and subtracting whole numbers.

Be careful...

Line up the decimal point and the columns

Fill in any blank decimal places with zeros.

Example One - Addition

What is the sum of 3.45 and 67.8? (Line up the columns. Fill in any blank decimal places with zeros.)

Answer:

3.45

+ 67.80

71.25

Example Two - Subtraction

What is the difference between 67.8 and 3.45? (Line up the columns. Fill in any blank decimal places with zeros.)

Answer:

67.80

– 3.45

64.35

Question - Novelty Contact Lenses

At c-r-a-z-y-e-y-e store, I bought 3 pairs of novelty contact lenses - Cats Eye for $58.95, Rainbow Eye for $38.78, and Green Dragon for $29.55. How much change did I receive from $150 cash?

Answer $22.72 to nearest cent; $22.70 cash

Question - Feeler Gauge

A feeler gauge is a tool used by engineers and car mechanics for measuring gap widths such as the gap in a spark plug. The six gauges have widths of 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm and 0.6 mm. Which combination of these would be used to measure a gap of 1.5 mm?