Difference between revisions of "1993 AJHSME Problems/Problem 9"

(Solution)
(Solution 2)
Line 20: Line 20:
 
==Solution 2==
 
==Solution 2==
 
By the chart, we can see that the "<math>*</math>" operation is actually multiplication modulo <math>5</math>. Thus, we can do <math>(2*4)*(1*3)\rightarrow(2\cdot4)\cdot(1\cdot3)=8\cdot3=24\rightarrow\boxed{\text{(D)}\ 4}</math>
 
By the chart, we can see that the "<math>*</math>" operation is actually multiplication modulo <math>5</math>. Thus, we can do <math>(2*4)*(1*3)\rightarrow(2\cdot4)\cdot(1\cdot3)=8\cdot3=24\rightarrow\boxed{\text{(D)}\ 4}</math>
 +
- JeffersonJ
  
 
==See Also==
 
==See Also==

Revision as of 19:44, 16 June 2022

Problem

Consider the operation $*$ defined by the following table:

\[\begin{tabular}{c|cccc} * & 1 & 2 & 3 & 4 \\ \hline 1 & 1 & 2 & 3 & 4 \\ 2 & 2 & 4 & 1 & 3 \\ 3 & 3 & 1 & 4 & 2 \\ 4 & 4 & 3 & 2 & 1 \end{tabular}\]

For example, $3*2=1$. Then $(2*4)*(1*3)=$

$\text{(A)}\ 1 \qquad \text{(B)}\ 2 \qquad \text{(C)}\ 3 \qquad \text{(D)}\ 4 \qquad \text{(E)}\ 5$

Solution 1

Using the chart, $(2*4)=3$ and $(1*3)=3$. Therefore, $(2*4)*(1*3)=3*3=\boxed{\text{(D)}\ 4}$.

Solution 2

By the chart, we can see that the "$*$" operation is actually multiplication modulo $5$. Thus, we can do $(2*4)*(1*3)\rightarrow(2\cdot4)\cdot(1\cdot3)=8\cdot3=24\rightarrow\boxed{\text{(D)}\ 4}$ - JeffersonJ

See Also

1993 AJHSME (ProblemsAnswer KeyResources)
Preceded by
Problem 8
Followed by
Problem 10
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
All AJHSME/AMC 8 Problems and Solutions

The problems on this page are copyrighted by the Mathematical Association of America's American Mathematics Competitions. AMC logo.png