Linear Inequalities
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SAT Math › Linear Inequalities
A rideshare company charges a $4 booking fee plus $1.75 per mile, and you have at most $20 to spend. Let $m$ be the number of miles you can ride. Which inequality represents this situation?
$1.75m+4\ge 20$
$1.75m+4\le 20$
$1.75m-4\le 20$
$4m+1.75\le 20$
Explanation
This question asks you to set up an inequality modeling the maximum spending on a rideshare with a $4 fee and $1.75 per mile, given at most $20 available. The total cost is 4 + 1.75m, and since you can spend up to $20, the inequality is 1.75m + 4 ≤ 20. Note that 'at most' includes equality, so use ≤ rather than <. A common error is using ≥, which would imply spending at least $20, but the situation requires no more than $20. Another pitfall is swapping the fee and per-mile rate, leading to incorrect expressions like choice C. When setting up inequalities from word problems, identify key phrases like 'at most' to determine the direction of the inequality symbol.
A number line shows a closed circle at $-1$ and shading to the right. Which inequality matches this graph?
$x<-1$
$x>-1$
$x\ge -1$
$x\le -1$
Explanation
This question requires matching a number line with a closed circle at -1 and shading right to the inequality. Closed circle includes the point, so ≥ or ≤. Right shading means greater than or equal to -1, x ≥ -1. A key error is using > with closed circle. Another is left-shading confusion. Note circle type and direction for precise matching.
Solve $7-\frac{1}{2}x\ge 1$ and choose the correct solution for $x$.
$x\le -12$
$x\ge -12$
$x\le 12$
$x\ge 12$
Explanation
This question requires solving 7 - (1/2)x ≥ 1 for x. Subtract 7: -(1/2)x ≥ -6. Multiply by -2, reversing: x ≤ 12. Verify with x=12: 7 - 6 =1 ≥1, true. A common error is not reversing when multiplying by negative. Another mistake is arithmetic errors in isolation. Explicitly note reversal when multiplying by negatives.
A recipe needs between 2 and 5 cups of flour, inclusive. Let $f$ be the number of cups of flour used. Which inequality represents the allowable values of $f$?
$2\le f\le 5$
$2<f\le 5$
$2\le f<5$
$2<f<5$
Explanation
This question asks for an inequality for flour f between 2 and 5 cups inclusive. 'Between inclusive' means 2 ≤ f ≤ 5. Use ≤ for both bounds since endpoints are included. A common error is using < > for exclusive, excluding 2 or 5. Another pitfall is mismatching bounds. Translate 'inclusive' to ≤ and ≥ for closed intervals.
Solve the compound inequality $3x+6\ge 0$ OR $2x-5<1$. Which statement describes all solutions?
$x<3$
$-2\le x<3$
$x\ge -2$
All real $x$
Explanation
This question requires solving 3x + 6 ≥ 0 or 2x - 5 < 1. First: x ≥ -2. Second: x < 3. The union covers all real x since intervals overlap completely. A common error is treating as 'and', giving -2 ≤ x < 3. Another mistake is incorrect solving of parts. For 'or' compounds, combine regions to see if they cover everything.
A phone plan costs $30 per month plus $0.10 per text message. If you want the bill to be no more than $45, let $t$ be the number of texts. Which inequality gives the possible values of $t$?
$30+0.10t\ge 45$
$0.10t-30\le 45$
$0.10t+45\le 30$
$30+0.10t\le 45$
Explanation
This question asks for an inequality for a phone bill of 30 + 0.10t ≤ 45. 'No more than' means ≤ for the upper limit. Subtract 30: 0.10t ≤ 15, but setup is key. A common error is using ≥, implying at least 45. Another pitfall is swapping fixed and variable costs. Read for limits like 'no more than' to set ≤ correctly.
Solve $4(x-3)\le 2x+10$. What is the solution set?
$x\ge 1$
$x\le 1$
$x\ge 11$
$x\le 11$
Explanation
This question requires solving 4(x - 3) ≤ 2x + 10 for x. Distribute: 4x - 12 ≤ 2x + 10. Subtract 2x: 2x - 12 ≤ 10. Add 12: 2x ≤ 22. Divide by 2: x ≤ 11. A common error is distributing incorrectly or forgetting to isolate x. When solving multi-step inequalities, perform operations step-by-step and check for reversal if negatives are involved.
A student has at least $45$ minutes to study and spends $x$ minutes on math plus $12$ minutes on vocabulary. Which inequality describes the possible values of $x$?
$x+12\ge 45$
$x+12\le 45$
$12-x\ge 45$
$x-12\ge 45$
Explanation
This question asks for an inequality where a student spends x minutes on math plus 12 on vocabulary, totaling at least 45 minutes. The total time is x + 12 ≥ 45. Subtract 12: x ≥ 33, but the question seeks the setup. A common error is using ≤, implying an upper limit instead of minimum. Another pitfall is subtracting 12 from x. Identify 'at least' to use ≥ in minimum requirement problems.
A number line shows an open circle at $6$ with shading to the left. Which inequality matches this graph?
$x\ge 6$
$x>6$
$x\le 6$
$x<6$
Explanation
This question requires matching a number line with an open circle at 6 and shading to the left to the correct inequality. Open circle means not included, so < or >. Left shading indicates less than 6, giving x < 6. A key error is interpreting as ≥6 due to misreading the shading direction. Another common mistake is using ≤ with the open circle. Pay attention to circle type and shading for accurate inequality matching.
Which value of $x$ satisfies the inequality $5-2x>11$?
$-4$
$0$
$4$
$-3$
Explanation
This question asks which value satisfies 5 - 2x > 11. Subtract 5: -2x > 6. Divide by -2, reversing the symbol: x < -3. Test x = -4: 5 - 2(-4) = 13 > 11, true. A common error is not reversing when dividing by negative, leading to x > -3. Another mistake is testing values without solving first. For inequalities with negatives, explicitly note the reversal to ensure correct testing of options.