See56.7 cause it is the correct one to the 20th
Answer:
40287600 = B. 4 x 
Step-by-step explanation:
<u>We first have to do the multiplication of the numbers given:</u>
19 * 2,120,400
=> 40287600
<u>Now we have to figure out how many digits are after the number 4:</u>
4, 0 2 8 7 6 0 0
7 digits
Meaning that we need an exponent of 7 for it to be in scientific notation, giving us with the answer B. 4 x
A= 30
Explanation: 88-58=30
Let's call the stamps A, B, and C. They can each be used only once. I assume all 3 must be used in each possible arrangement.
There are two ways to solve this. We can list each possible arrangement of stamps, or we can plug in the numbers to a formula.
Let's find all possible arrangements first. We can easily start spouting out possible arrangements of the 3 stamps, but to make sure we find them all, let's go in alphabetical order. First, let's look at the arrangements that start with A:
ABC
ACB
There are no other ways to arrange 3 stamps with the first stamp being A. Let's look at the ways to arrange them starting with B:
BAC
BCA
Try finding the arrangements that start with C:
C_ _
C_ _
Or we can try a little formula; y×(y-1)×(y-2)×(y-3)...until the (y-x) = 1 where y=the number of items.
In this case there are 3 stamps, so y=3, and the formula looks like this: 3×(3-1)×(3-2).
Confused? Let me explain why it works.
There are 3 possibilities for the first stamp: A, B, or C.
There are 2 possibilities for the second space: The two stamps that are not in the first space.
There is 1 possibility for the third space: the stamp not used in the first or second space.
So the number of possibilities, in this case, is 3×2×1.
We can see that the number of ways that 3 stamps can be attached is the same regardless of method used.
DC :AB=3:2 can be written as
DC/AB=3/2
Then you can get the answers easily
