Question

If $3\le 3t-18\le 18,$ then which one of the following is true?

• A. $15\le 2t+1\le 20$
• B. $8\le t<12$
• C. $8\le t+1\le 13$
• D. $21\le 3t\le 24$
• E. $t\le 7$ or $t\ge 12$

Answer 1

Answer: (C)

We have $3\le 3t-18\le 18$
$\Rightarrow$ $3+18\le 3t\le 18+18$
$\Rightarrow$ $21\le 3t\le 36$
$\Rightarrow$ $7\le t\le 12$
$\Rightarrow$ $8\le t+1\le 13$