Fractions addition: slideshare
I use this quick method for adding two fractions of moderate size with Science students who need to revise basic numeracy quickly. The method is less efficient with large numerators and denominators and with denominators that have large highest common factors.
Most ‘everyday’ fractions have numerators in the 2, 4, 8, 16 sequence or thirds, sixths and ninths and the fifths and tenths. Obscure large prime denominators are unusual!
I do teach the ‘standard’ methods as well, and I like to use the prime factor method to find the lowest common denominator when the time allocation allows.