What is the rational number equivalent to __ 3.24?
1 answer:
Answer:
Step-by-step explanation:
Think of a rational number as a fraction. The definition of a rational number is that it is the ratio of integers that, when divided, is either an integer, a decimal that terminates, or a decimal that repeats. 6/3 = 2 (6/3 is a rational number that divides to 2); 1/2 = .5 (1/2 is a rational number that divides to .5 which is a terminating decimal, meaning it ends); 1/3 = .33333333 (1/3 is a rational number that divides to .3333333 which is a repeating decimal). If we want to express 3.24 as a rational number, let's first put it into fraction form. The 4 in .24 is in the hundredths place, so as a fraction, .24 is 24/100. Check this on your calculator. Divide 24 by 100 and you get .24. So now what we have is
Now express that mixed fraction as an improper and you're done. 3 times 100 is 300; 300 + 24 = 324. Put that back over 100 and your rational number is 324/100. Check that on your calculator, as well, just to see that it's true.
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Explanation:
Each row in Pascal's triangle is a listing of the values of nCk = n!/(k!(n-k)!) for some fixed n and k in the range 0 to n. nCk is <em>the number of combinations of n things taken k at a time</em>.
If you consider what happens when you multiply out the product (a +b)^n, you can see where the coefficients nCk come from. For example, consider the cube ...
(a +b)^3 = (a +b)(a +b)(a +b)
The highest-degree "a" term will be a^3, the result of multiplying together the first terms of each of the binomials.
The term a^b will have a coefficient that reflects the sum of all the ways you can get a^b by multiplying different combinations of the terms. Here they are ...
- (a +_)(a +_)(_ +b) = a·a·b = a^2b
- (a +_)(_ +b)(a +_) = a·b·a = a^2b
- (_ +b)(a +_)(a +_) = b·a·a = a^2b
Adding these three products together gives 3a^2b, the second term of the expansion.
For this cubic, the third term of the expansion is the sum of the ways you can get ab^2. It is essentially what is shown above, but with "a" and "b" swapped. Hence, there are 3 combinations, and the total is 3ab^2.
Of course, there is only one way to get b^3.
So the expansion of the cube (a+b)^3 is ...
(a +b)^3 = a^3 + 3a^2b +3ab^2 +b^3 . . . . . with coefficients 1, 3, 3, 1 matching the 4th row of Pascal's triangle.
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In short, the values in Pascal's triangle are the values of the number of combinations of n things taken k at a time. The coefficients of a binomial expansion are also the number of combinations of n things taken k at a time. Each term of the expansion of (a+b)^n is of the form (nCk)·a^(n-k)·b^k for k =0 to n.
