MathDB

12

Part of 2022 AMC 10

Problems(2)

Halloween Candy

Source: 2022 AMC 10A #12 / 2022 AMC 12A #9

11/11/2022
On Halloween 31 children walked into the principal's office asking for candy. They can be classified into three types: Some always lie; some always tell the truth; and some alternately lie and tell the truth. The alternaters arbitrarily choose their first response, either a lie or the truth, but each subsequent statement has the opposite truth value from its predecessor. The principal asked everyone the same three questions in this order.
"Are you a truth-teller?" The principal gave a piece of candy to each of the 22 children who answered yes.
"Are you an alternater?" The principal gave a piece of candy to each of the 15 children who answered yes.
"Are you a liar?" The principal gave a piece of candy to each of the 9 children who answered yes.
How many pieces of candy in all did the principal give to the children who always tell the truth?
<spanclass=latexbold>(A)</span>7<spanclass=latexbold>(B)</span>12<spanclass=latexbold>(C)</span>21<spanclass=latexbold>(D)</span>27<spanclass=latexbold>(E)</span>31<span class='latex-bold'>(A) </span>7\qquad<span class='latex-bold'>(B) </span>12\qquad<span class='latex-bold'>(C) </span>21\qquad<span class='latex-bold'>(D) </span>27\qquad<span class='latex-bold'>(E) </span>31
AMCAMC 10AMC 122022 AMC2022 AMC 10a2022 AMC 12Alogic
Sum of dice is 7

Source: 2022 AMC 10B P12

11/17/2022
A pair of fair 66-sided dice is rolled nn times. What is the least value of nn such that the probability that the sum of the numbers face up on a roll equals 77 at least once is greater than 12\frac{1}{2}?
<spanclass=latexbold>(A)</span>2<spanclass=latexbold>(B)</span>3<spanclass=latexbold>(C)</span>4<spanclass=latexbold>(D)</span>5<spanclass=latexbold>(E)</span>6<span class='latex-bold'>(A) </span> 2 \qquad <span class='latex-bold'>(B) </span> 3 \qquad <span class='latex-bold'>(C) </span> 4 \qquad <span class='latex-bold'>(D) </span> 5 \qquad <span class='latex-bold'>(E) </span> 6
probabilityAMCAMC 102022 AMC2022 AMC 10BDice