A jar contains only red beads and white beads, 48 beads in total. If one bead is selected at random, the probability that it is red is 38. How many white beads must be added to the jar so that the probability of selecting a red bead becomes 14?

SAT Probability and conditional probability Practice Question 9 (Medium)

Question bank / Probability and conditional probability

Math · Problem-Solving and Data AnalysisMedium

A jar contains only red beads and white beads, $48$ beads in total. If one bead is selected at random, the probability that it is red is $\frac{3}{8}$ . How many white beads must be added to the jar so that the probability of selecting a red bead becomes $\frac{1}{4}$ ?

Student-produced response: enter your answer.

Show answer and explanation

Answer: 24

The jar has $\frac{3}{8} \times 48 = 18$ red beads. After adding $n$ white beads, $\frac{18}{48 + n} = \frac{1}{4}$ , so $48 + n = 72$ and $n = 24$ .

Answering $72$ gives the new total number of beads, not the number of beads added.

Ask Owl about this question Next question

Got it wrong? On SAT Owl, Owl looks at the answer you chose and explains the exact mistake, then gives you similar questions until it sticks. Get your predicted SAT score free.