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<p>I don't have the answer, and can someone explain how to do it? thanks a lot :)</p>
<p>I might be pulling this outta my ass, but here we go anyway…</p>
<p>a/b = 1.25</p>
<p>This tells me that I can plug in values of b and multiply them by 1.25 in order to find out what a is equal to. The first option is 800. Let’s try it. 800 * 1.25 = 1000. This means a = 1000. Now, a + b must be LESS than 1800 (as stated earlier in the question). But a is 1000 and b is 800, so together they make 1800… so it’s a no go</p>
<p>Next option, b = 798. Let’s see… 798 * 1.25 = 997.5. So a = 997.5
Now, a + b must LESS than 1800. So 798 + 997.5 = 1795.5.
1795.5 is pretty darn close to 1800. Seems good so far.</p>
<p>Now, any other option lower than 798 will only yield lower results, so choice B is the greatest option.</p>
<p>EDIT: this answer’s wrong… look at knowthestuff’s answer</p>
<p>No need to try estimates use the second equation to relate a and b i.e a=1.25b now put it in the first inequality i.e b+1.25b<1800 on solving 2.25b<1800 therefore b<800…cheers</p>
<p>a/b = 1.25 (a = 1.25 b)
OR
a/b = 5/4<br>
Since a and b must be integers, the 4 in the denominator is a tip-off that b is a multiple of 4.</p>
<p>a + b < 1800
1.25 b + b < 1800
2.25 b < 1800
b < 800
Therefore choice A is out.</p>
<p>The biggest multiple of 4 in the remaining choices is 796. Plug in 796 for b and you get a = 995, which is an integer.
a + b = 1791, which satisfies the a + b < 1800 requirement.</p>
<p>Answer: C</p>
<p>Oh… yeah… ^ is right</p>
<p>knowthestuff’s answer is correct and you can also use johnny’s, his only fault was that the question said a and b are positive integers and 997.5 is not an integer. But if you knew that, you could keep substituting and you would also get C).</p>
<p>Yup… I only recently started preparing for the SAT and I can already tell that it’s imperative that you underline the word integer when you see it in a question. Although the question OP posted was made by another company, TCB likes to do this some times too. It’s happened to me a bunch of times</p>
<p>This is a great question, may I ask which prep book you’re using or where you got this problem from? Thanks.</p>
<p>A very similar CB question is discussed here:
<a href=“collegeboard questions - SAT Preparation - College Confidential Forums”>collegeboard questions - SAT Preparation - College Confidential Forums;
<p>Using the same approach:
a/b=5/4
a=5n, b=4n, where n is an integer
a+b<1800
5n+4n<1800
9n<1800
n<200
To maximize b let n=199
b=4*199
b=796</p>