Difference between revisions of "1966 AHSME Problems/Problem 25"

(Created page with "== Problem == If <math>F(n+1)=\frac{2F(n)+1}{2}</math> for <math>n=1,2,\cdots</math> and <math>F(1)=2</math>, then <math>F(101)</math> equals: <math>\text{(A) } 49 \quad \text{(...")
 
m (Solution)
 
(3 intermediate revisions by 2 users not shown)
Line 5: Line 5:
  
 
== Solution ==
 
== Solution ==
 +
Notice that <math>\frac{2F(n)+1}{2}=F(n)+\frac{1}{2}.</math>
  
 +
This means that for every single increment <math>n</math> goes up from <math>1</math>, <math>F(n)</math> will increase by <math>\frac{1}{2}.</math> Since <math>101</math> is <math>100</math> increments from <math>1</math>, <math>F(n)</math> will increase <math>\frac{1}{2}\times100=50.</math>
 +
 +
Since <math>F(1)=2,</math> <math>F(101)</math> will equal <math>2+50=\boxed{\text{(D)} \ 52}.</math>
 +
 +
 +
Solution by davidaops.
  
 
== See also ==
 
== See also ==

Latest revision as of 16:06, 5 December 2018

Problem

If $F(n+1)=\frac{2F(n)+1}{2}$ for $n=1,2,\cdots$ and $F(1)=2$, then $F(101)$ equals:

$\text{(A) } 49 \quad \text{(B) } 50 \quad \text{(C) } 51 \quad \text{(D) } 52 \quad \text{(E) } 53$

Solution

Notice that $\frac{2F(n)+1}{2}=F(n)+\frac{1}{2}.$

This means that for every single increment $n$ goes up from $1$, $F(n)$ will increase by $\frac{1}{2}.$ Since $101$ is $100$ increments from $1$, $F(n)$ will increase $\frac{1}{2}\times100=50.$

Since $F(1)=2,$ $F(101)$ will equal $2+50=\boxed{\text{(D)} \ 52}.$


Solution by davidaops.

See also

1966 AHSME (ProblemsAnswer KeyResources)
Preceded by
Problem 24
Followed by
Problem 26
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 26 27 28 29 30
All AHSME Problems and Solutions

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