+0

# help plz

0
79
3

One day, Alexis decides to write down all the numbers from 1 to 999, inclusive.
a) How many digits did Alexis write, in total?

b) Alexis chooses one of the digits written down at random. What is the probability that the chosen digit is a 7?

c) What is the sum of all the digits that Alexis wrote down?

Jan 26, 2020

#1
0

a) If you are counting the DIGITS of the number 1 to 999, then there are =2,889 digits between 1 and 999.

b) There are 300 "7s" between 1 and 999, including duplicates such as:77, 777......etc. Therefore, the probability that a randomly chosen number is a 7 =300 /2,889 =~ 10.38 %

c) The sum of all the digits in a) above = 13,500.

Jan 26, 2020
#2
0

One day, Alexis decides to write down all the numbers from 1 to 999, inclusive.
a) How many digits did Alexis write, in total?

b) Alexis chooses one of the digits written down at random. What is the probability that the chosen digit is a 7?

c) What is the sum of all the digits that Alexis wrote down?  Jan 26, 2020
#3
0

Omi67:

There are 19 "sevens" between 10 - 99.

17, 27, 37, 47, 57, 67, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 87, 97 =19 "Sevens"

There are 300 "sevens" between 1 and 999.

Jan 26, 2020