GRE Sample Test 2 Quantitative Reasoning 1

Substitute 6 for x in the equation, ${\mathit{s}}_{\mathit{x}}$ = $2{\mathit{s}}_{\mathit{x}-1}+{\mathit{s}}_{\mathit{x}-2}$ and work carefully from there. ${\mathit{s}}_6$ = $2{\mathit{s}}_{6-1}+{\mathit{s}}_{6-2}$ , which simplifies to ${\mathit{s}}_6$ = $2{\mathit{s}}_5+{\mathit{s}}_4$. However, you don’t know ${\mathit{s}}_5$ or ${\mathit{s}}_4$. Use the equation to find these missing terms. ${\mathit{s}}_4$ = $2{\mathit{s}}_3+{\mathit{s}}_2$. and the problem tells you ${\mathit{s}}_2$ and ${\mathit{s}}_3$ are equal to 2. ${\mathit{s}}_4$ = (2 × 2) + 2, which is 6. Now you need to find ${\mathit{s}}_5$. Using the equation, you get ${\mathit{s}}_5$ = (2 × 6) + 2, which is 14. Now that you know ${\mathit{s}}_5$ and ${\mathit{s}}_4$, go back to your original equation, ${\mathit{s}}_6$ = $2{\mathit{s}}_5+{\mathit{s}}_4$, and ${\mathit{s}}_6$ = (2 × 14) + 6, which is 34.