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Word Problem - Number of Floors in Apartment Building











































The elevator of an apartment building has no button which has the digit 4.

If the numbers start with 1 and the highest number is 85, how many floors are there in this apartment building?

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Historical Note: Tetra phobia is the superstitious fear of the number 4. The number 4 is considered so unlucky that the council in Richmond Hill, Ontario voted to eliminate the use of a single 4 in all new house numbers. Apparently the ban begins in the year 2013. However, double digit 4's, such as 44 are OK.

(Tetra phobia is similar to Triskaidekaphobia, which is the irrational fear of the number 13.)

Comments for Word Problem - Number of Floors in Apartment Building

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Aug 18, 2013
Number of Floors
by: Staff


Answer


I assume the number of every floor containing the 4 digit does not exist.

There are 18 floors which contain the number 4.

These are:

4
14
24
34
40
41
42
43
44
45
46
47
48
49
54
64
74
84


Apartment building eliminates 18 floors by not using the number  four




The number of floors which do not contain the number 4:

# Floors = 85 - 18 = 67

final answer: 67 floors


 Apartment building has 67 floors







Thanks for writing.

Staff
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