total weight

Question

 Erin orders a book which weighs 1 1/4 pounds and a CD which weighs 1/5 of a pound. They are shipped in a box which weighs 3/10 of a pound empty. What is the total weight of the box with the book and CD?

Answer 1

Total Weight = Weight of the book + Weight of the CD + Weight of the box

 

Total Weight = 1 ¹/₄ pound + 1/5 pound + 3/10 pound

 

Total Weight = 5/4 + 1/5 + 3/10

 

To add these fractions, you need to put them over a common denominator.  To do that, find the least common multiple of 4, 5, and 10.  Below is a table of the multiples.  The least multiple they have in common is 20, shown in orange.  So use 20 as your least common denominator.

 

           1      2      3      4     5      6     7

4 x      4     8     12    16   20    24   ...

5 x      5    10    15    20   25    30   ...

10 x   10   20   30    40    50    60   ...

 

Can you finish it from here?