Final answer:
Mikey spent a total of 1 hour and 37.5 minutes on her mathematics and science homework, by first converting the fractions to have a common denominator and then adding the times together.
Step-by-step explanation:
To calculate the total time Mikey spent on her mathematics and science homework, we need to add the time she spent on each subject together. Mikey worked on her mathematics homework for 3/4 hour and her science homework for 7/8 hour. To add these fractions, they must have a common denominator.
Let's convert 3/4 to 6/8 so that both fractions have the denominator of 8. Now we can add the two times:
6/8 hour (mathematics homework)
+ 7/8 hour (science homework)
= 13/8 hours
Since 8/8 equals 1 hour, 13/8 hours can be converted into 1 hour and 5/8 of an hour. Since 5/8 of an hour is 37.5 minutes (as there are 60 minutes in an hour), Mikey spent a total of 1 hour and 37.5 minutes doing her homework.