SOLUTION: 8=56 7=42 6=30 5=20 3=? What does 3 equal?

Algebra.Com
Question 777580: 8=56
7=42
6=30
5=20
3=?
What does 3 equal?

Found 8 solutions by oscargut, solver91311, tinbar, nyc_function, gurungsantosh, MathTherapy, acubed1234, mbessearch:
Answer by oscargut(2103)   (Show Source): You can put this solution on YOUR website!
3x2 = 6
I can help you with more questions at: mthman@gmail.com
Thanks


Answer by solver91311(24713)   (Show Source): You can put this solution on YOUR website!




John

Egw to Beta kai to Sigma
My calculator said it, I believe it, that settles it
The Out Campaign: Scarlet Letter of Atheism


Answer by tinbar(133)   (Show Source): You can put this solution on YOUR website!
The answer is 6.
Here's the pattern:
When you see "x = y" really, y = x * (x-1)
56 = 8 * 7
42 = 7 * 6
30 = 6 * 5
...
When you get to 3=? you can see it should be 3 * 2 which is 6

Answer by nyc_function(2741)   (Show Source): You can put this solution on YOUR website!
After 5 x 4 = 20, comes 4 x 3 = 12 and
then 3 x 2 = 6.

Answer by gurungsantosh(1)   (Show Source): You can put this solution on YOUR website!
56-(8+7)+1=42
42-(7+6)+1=30
30-(6+5)+1=20
20-(5+3)+1=13
answer is 13 guys

Answer by MathTherapy(10552)   (Show Source): You can put this solution on YOUR website!
8=56
7=42
6=30
5=20
3=?
What does 3 equal?

8(8 - 1) = 56
7(7 - 1) = 42
6(6 - 1) = 30
5(5 - 1) = 20
4(4 - 1) = 12
3(3 - 1) = 6

Answer by acubed1234(5)   (Show Source): You can put this solution on YOUR website!
It turns out the ‘?’ can be whatever we want it to be!
Allow me to illustrate. Take for example, f(x)=(1/40)x^4-(13/20)x^3+(291/40)x^2-(553/20)x+42, and evaluate f(8), f(7), f(6), f(5), f(3). It turns out that:
f(8)=56,
f(7)=42,
f(6)=30,
f(5)=20,
f(3)=9.
Wait, what sorcery is this? Turns out that although the popular rule f(x)=x(x-1), which gives f(x)=6, satisfies the known values in the sequence, that f(x)=(1/40)x^4-(13/20)x^3+(291/40)x^2-(553/20)x+42 also satisfies them–except with a different value of f(3)!
Here’s another one that also works but gives f(3)=12:
f(x)=(1/20)x^4-(13/10)x^3+(271/20)x^2-(543/10)x+84
And here is one where f(3)=π
f(x)=(1/120)(π-6)x^4-(13/60)(π-6)x^3+(1/120)(251π-1386)x^2+(1/60)(3138-533π)x+14(π-6)
Finally, in general if you want the ‘?’=k, i.e., f(3)=k where k is the value of your choice, then
(1/120)(k-6)x^4-(13/60)(k-6)x^3+(1/120)(251k-1386)x^2+(1/60)(3138-533k)x+14(k-6)
More details here: https://www.scribd.com/doc/260182194/Elementary-Sequences
For a non-polynomial rule see here: http://i.imgur.com/BHkg0Ad.png

Answer by mbessearch(2)   (Show Source): You can put this solution on YOUR website!
The answer is 3. Equal means equals. While the various functions and formulas displayed elsewhere in answer would be reasonable if shown, without them, there are four wrong answers. One of the beauties of Math is that it is precise. Do not use equals unless you mean equals.
RELATED QUESTIONS

8=56 7=42 6=30 5=20 3=?what does 3... (answered by rfer,acubed1234)
8=56 7=42 6=30 5=20... (answered by checkley79,acubed1234)
2 3 4 15 12 3 4 5 28 20 4 5 6 X 30 5 6 7 66 42 6 7 8 91 56 Find... (answered by Tatiana_Stebko)
what does 7/20 + 3/9 equal ? (answered by josgarithmetic)
After simplifying the matrix operation below, what does a32 equal? 5 12... (answered by jim_thompson5910)
Which set of three numbers can be used to make a right triangle? A 3, 4, 5 B 4, 5, 6 (answered by Alan3354)
1. If 6^x = 5, what does 6^-2x equal? 2. if 7^x=3, what does 7^-2x... (answered by ikleyn)
2a-4a=1 What does a equal -y+6-5y=18 What does y equal 6-z-4z=-4 What does z equal (answered by Nate)
3 5/8 divied by n = 4 5/6...what does n equal (answered by ReadingBoosters)