Answer:
Sea level is 0 meters. A cliff by the ocean is 12 meters above sea level. Around that area, the seafloor is 8 meters below sea level. How many meters is the top of the cliff to the seafloor?
How to solve:
8 below zero is -8
The expression 12 - (-8) is the same as the expression 12 + 8
12 + 8 = 20
20 meters
Answer: D) 12
Step-by-step explanation:
If the customer buys 4 pencils he will get the 5th one free.
This means, in every 5 pencils, he is getting one free pencil. 60 pencils can be split into 12 groups of 5 pencils each. In each group he is getting 1 free pencil, so in 12 groups, the customer will get 12 free pencils.
So, we can say that if the customer buys 60 pencils on sale, he will get 12 of them free.
The number of possible combinations is given by
... C(18, 3) = 18!/(3!(18-3)!) = 18·17·16/(3·2·1) = 816 . . . . possible combinations
_____
There are 18 ways to choose the first one; 17 ways to choose the second one, and 16 ways to choose the 3rd one. The same 3 students can be chosen in any of 3! = 6 different orders, so the product 18·17·16 must be divided by 6 to get the number of possible combinations in which order doesn't matter.
72*12 = 2*2*2*2*2*3*3*3 = 2^5*3^3
