**Name_______________________________________________Date_________________________
Mathematics Problem Solving
Volume 4, Number 30, May 3, 1999
www.rhlschool.com**

**Probability**

1. There are 20 students in Mrs.
Church’s fourth grade. Mrs. Church had them all put their
names on an index card. She’ll draw a name to see who will
get to teach a math lesson on Friday. Carlos hopes he’ll be
chosen. **What chance does he have?**

2. Mr. El just bought a box of Girl Scout
cookies. He told his class, “I’d like to eat this
box of thin mints all by myself. It’s one of my most
treasured annual traditions! But I could share the cookies with all of
my dear students. It’s only fair that I give you a chance to
help me eat them. Here’s what we’ll do: There are
29 blue marbles in this cloth bag. There is one red marble.
I’ll have David reach in, without
peeking, and pull out a marble,. If it’s a red
marble, I’ll share. If it’s blue, I’ll be
forced to eat them all.

**Under this plan, what
chance does the class have to share the cookies? **

3. Mr. El then admitted that he really was
going to give the kids a better chance. There were actually 20 blue
marbles and 20 red marbles in the bag. That would give the kids a
better chance to win.

**What was the chance that
they would get to share the cookies under this plan?**

4. David drew a blue marble. But Mr. El
felt bad when he saw the sad faces on his 22 students’ faces.
“OK, I’ll give you guys one more chance,”
he said. “Each student can take out one marble. If anyone
gets a red marble, I’ll share.”

**What chance did the class
have of winning this time?**

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