Basic College Mathematics (10th Edition)

(answers vary) The main reason in not getting $1$ as an answer is that you made a mistake in the addition of the fractions. Some possible mistakes are: (1) You made a mistake in converting some fractions to a fraction whose denominator is 20 (the LCD). (2) After making the fractions similar using their LCD of 20, you made a mistake in adding the numerators. (3) You made a mistake of adding the numerators together and adding the denominators together to get $\frac{7}{29}$.
In Exercise 21, if you added the fractions for the groups and did not get $1$ as answer, then you must have made a mistake in the addition. Some possible reasons are: (1) You made a mistake in converting some fractions to a fraction whose denominator is 20 (the LCD); (2) After making the fractions similar using their LCD of 20, you made a mistake in adding the numerators; or (3) You made a mistake of adding the numerators together and adding the denominators together to get $\frac{7}{29}$.