Unit 4 · Statistics and Probability

Half Are Red — How Many Yellow?

Lesson 5 of 8

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Total = 36, blue = 16, P(red) = 1/2. Red = 1/2 × 36 = 18. Yellow = 36 − 16 − 18 = 2.

Chapters

0:00Introduction
0:22The Question
0:58Unlocking the Red Marble Count via Fractions
1:27Setting Up the Total Distribution Model
1:51Calculating the Missing Balance
2:16Exam Strategy — The Subtraction Compliment Shortcut
2:54Confirming the Final Option

Question

Amrita has a bag of 36 marbles. Some are blue, some are red and the rest are yellow.

There are 16 blue marbles in the bag.

If she takes out a marble without looking, the probability that it is red is 12\frac{1}{2}.

How many yellow marbles are in the bag?

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