what is the probability that a random number generator generates a 3 digit number where the 1st digit is prime and the number is multiple of ten

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samhouston | Middle School Teacher | (Level 1) Associate Educator

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The first digit is prime, so the choices are:
2, 3, 5, and 7

There are no restrictions on the second digit, so the choices are:
0, 1, 2, 3, 4, 5, 6, 7, 8, and 9

The number is a multiple of 10, so the third digit must be:
0

To find the number of 3-digit numbers that meet the above criteria, multiply the number of choices for each digit.

First digit:  4 choices
Second digit:  10 choices
Third digit:  1 choice

4 * 10 * 1 = 40

With no restrictions, there are 1,000 possible combinations.
10 * 10 * 10 = 1,000

The probability will be 40 out of 1,000.

Answer:  40/1,000 = 0.04 = 4%

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