Answer:
66
Step-by-step explanation:
If there are <em>n</em> students, then the number of pairs is 
.
With 12 students, 
pairs can be formed.
The reason the formula works is this: Each of the 12 students can be paired with 11 other students (no student is paired with him/her self). But counting 12 x 11 = 132 counts each pair <u>twice</u>. Example: student A can be paired with student B,..., student B can be paired with student A. The pair was counted two times.
See the attached image that shows pairings of 5 students. There are
5(5 - 1)/2 = 5(4)/2 = 10 pairs.
The answer is B: 6 cm. You can use guess-and-check method, and plug the possible different answers into the equation x(x+6)=72, x stands for the width.
Reorder the terms
112 + 3x = 100 + 5x
112 + 3x + (-5x) = 100 + 5x + (-5x)
Combine the like terms
5x + (-5x) = 0
112 + (-2x) = 100 + 0
112 + (-2x) = 100
112 + (-112) + (-2x) = 100 + (-112)
Combine like terms again
112 + (-112) =0
0 + (-2x) = 100 + (-112)
100 + (-112) = (-112) = (-12)
-2x = -12
-12 / -2 = 6
x = 6 <span>✓</span>
Check your work
3 * 6 + 112 = 130
5 * 6 + 110 = 130
130 = 130 ✓
7.8456 x 10^(-4)
this means you move the decimal place to the left 4 places to get the actual value
Okay, Jackie starts with 350 mailboxes, but has delivered to 150, so she only has to deliver to 200 more. She can deliver to 50 mailboxes per hour. So 200/50 = 4. The answer is 4 hours.
