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# 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?

. 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?

### 2 Answers by Expert Tutors

Michael V. | Selected at Instructor of the Year and Master Training SpecialistSelected at Instructor of the Year and M...
4.9 4.9 (62 lesson ratings) (62)
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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

Paul M. | Learn "how to" do the math and why the "how to" works!Learn "how to" do the math and why the "...
5.0 5.0 (1 lesson ratings) (1)
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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.