Last night Vivian spent 90 minutes doing homework, 2/3 hour reading, and 480 seconds fixing her lunch. How many more minutes did she spend doing her homework than she did reading and making her lunch

42 minutes

Step-by-step explanation:

We make sure all units are consistent before we make subtractions.

She spent 2/3 hours reading. 1 hour is 60 minutes, 2/3 hours reading = 2/3 * 60 = 40 minutes

She spent 480 seconds fixing lunch. 1 minute = 60 seconds, 480 seconds = 480/60 = 8 minutes

Hence, she spent 8 minutes fixing lunch and 40 minutes reading.

The number of minutes she spent doing her homework more than sleeping and reading is 90 - 40 - 8 = 42 minutes

42 minutes

Step-by-step explanation:

Vivian spent 90 minutes for homework,

2/3 of an hour = 2/3*60=40 minutes (time spent on reading) and

480 seconds ~ (480/60) for fixing her lunch

Combined minutes of reading and fixing her lunch = 8+40=48 minutes

Therefore, minutes spent on more on doing homework than fixing lunch and reading = 90-48=42 minute.