Solve this and you are a genius

• September 12th 2008, 06:10 AM
hotgal24
Solve this and you are a genius
http://img148.imageshack.us/img148/60/sepppnm3.jpg
What is the solution?
-*geniuises is not the answer to all question but the question to all answer*
• September 12th 2008, 08:29 AM
Henderson
Start by noticing that algebraically, your statement translates to :
$2 < \frac{88+n}{19+n} < 7$ (Do you see why?)

We'll solve the left side first:
$2 < \frac{88+n}{19+n}$
$2(19+n) < 88+n$ (Since n is positive, 19+n is also positive, and we don't need to worry about direction of the inequality.)
$38+2n < 88+n$
$n < 50$

On the right side:
$\frac{88+n}{19+n} < 7$
$88+n < 7(19+n)$
$88+n < 133+7n$
$-45 < 6n$
$-7.5 < n$

So $-7.5 < n < 50$. Since you said n is a positive integer, we'll adjust to $0 < n < 50$, of which there are 49 of them (0 and 50 aren't included).
• September 12th 2008, 09:14 AM
courteous
Quote:

Originally Posted by Henderson
Start by noticing that algebraically, your statement translates to :
$2 < \frac{88+n}{19+n} < 7$ (Do you see why?)

I don't see why. (Wondering) Please explain.
• September 12th 2008, 10:02 AM
Soroban
Hello, hotgal24!

Quote:

Find the number of possible positive integers $n$ such that

there are exactly two positive integers between $\frac{88+n}{19+n}$ and $\frac{88}{19}$

Since $\frac{88}{19} \:\approx\:4.63$, the two positive integers are 3 and 4

. . and: . $\frac{88+n}{19+n} \:>\:2 \quad\Rightarrow\quad n \:<\:50$

Therefore: . $n \:=\:1,2,3, \hdots 49$

. . There are 49 possible values of $n.$