2000 AMC 10 Problem 3

Question

Each day, Jenny ate

20\%

of the jellybeans that were in her jar at the beginning of that day. At the end of the second day,

32

remained. How many jellybeans were in the jar originally?

40

50

55

60

75

Eating

20\%

leaves

80\%

of the jellybeans at the end of each day

If

x

is the original amount, then

(0.8)^2 x = 32

Since Jenny eats

20\%

each day,

80\%

remain at the end of each day.

If

x

is the original number, then

(0.8)^2 x = 0.64x = 32,

so

x = 50.

Thus, the correct answer is B.

Problem 3 in other years