We use cookies to personalise content and advertisements and to analyse access to our website. Furthermore, our partners for online advertising receive pseudonymised information about your use of our website. cookie policy and privacy policy.
 
+0  
 
+1
237
1
avatar+814 

Assume every 7-digit whole number is a possible telephone number except those that begin with 0 or 1. What fraction of telephone numbers begin with 9 and end with 0?

 Jun 3, 2018
 #1
avatar+4299 
+1

We have 7 slots for our options because there are 7 digits.

 

_ _ _ _ _ _ _ and the problem says that the telephone number cannot start with 0 or 1, we have:

 

8*10*10*10*10*10*10=8*10^6=8,000,000

8 digits for the first slot, excluding 0 or 1.

 

Now, the problem is asking us to find the fraction of telephone numbers begin with 9 and end with 0.

 

So, we have 1*10*10*10*10*10*1=1*10^5=100,000.

 

Thus, the fraction is: \(\frac{100000}{8000000}=\boxed{\frac{1}{80}}\)

smileysmiley

.
 Jun 3, 2018

10 Online Users