The answer to this is .5 or 1/2.
Given:
Total number of senior students = 600
60% went on the senior trip.
One room was reserved for every 4 students.
To find:
The total number of reserved rooms.
Solution:
60% went on the senior trip from total 600 students. So, number of students who went on tripe is

Now, one room was reserved for every 4 students. So,



Therefore, the required number of reserved rooms were 90.
I think the third one on both part a and b can't be used to find the answer
42100000, so this is in scientific notation.
Step 1:
Convert the electricity per hour in kilowatts,
Electricity per hour = 20 watts
=20/1000 kilo,watts
Step 2:
The electricity consumes in 5 hour is ,
Electricity in 5 hour = 5x 20/1000 kilo watts.
Obtain the cost as,
=5x20/1000x10
=1 Cent
Answer: =1 Cent
Please mark brainliest
<em><u>Hope this helps.</u></em>