7. Kim works on social studies homework for 2 2 hours. Then, she works on math homework for 1 1/4. How many total hours does Kim spend doing homework?

Question

. Kim works on social studies homework for 2 2/5 hours. Then, she works on math homework for 1 1/4. How many total hours does Kim spend doing homework?

Answer 1

Convert the mixed numbers to improper fractions, find least common denominator, add, and then convert back to mixed number.

 

2 2/5 + 1 1/4

12/5 + 5/4

48/20 + 25/20

73/20

3 13/20

 

Answer 2

This problem is asking you to add the 2 mixed numbers: 1 1/4 + 2 2/5.

 

It is usually easier to convert mixed numbers to improper fractions or decimals.

 

To practice your fractions: 5/4 + 12/5

 

if you know how to "cross multiply", you will immediately get (25 + 48)/20 = 73/20 = 3 13/20

 

Otherwise to get the common denominator,  compute the least common multiple of 5 and 4 which you will find to be 20; this is your common denominator.

 

There are several ways to use the common denominator to get your answer.  Here is one.

 

Multiply each fraction by 20/20 to get (5*20/(4*20) +  (12*20)/(5*20) = (5*5)/20 + (12*4)/20 = (25 + 48)/20 as before.