Question:
In a certain town $25\%$ families own a cell phone, $15\%$ families own a scooter and $65\%$ families own neither a cell phone nor a scooter. If $1500$ families own both a cell phone and a scooter, then the total number of families in the town is
In a certain town $25\%$ families own a cell phone, $15\%$ families own a scooter and $65\%$ families own neither a cell phone nor a scooter. If $1500$ families own both a cell phone and a scooter, then the total number of families in the town is
Updated On: Jun 8, 2024
- $10,000$
- $20,000$
- $30,000$
- $40,000$
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The Correct Option is C
Solution and Explanation
Let the total population of town be $ x $ .
$ \therefore $ $ \frac{25x}{100}+\frac{15x}{100}-1500+\frac{65x}{100}=x $
$ \Rightarrow $ $ \frac{105x}{100}-x=1500 $
$ \Rightarrow $ $ \frac{5x}{100}=1500 $
$ \Rightarrow $ $ x=30000 $
$ \therefore $ $ \frac{25x}{100}+\frac{15x}{100}-1500+\frac{65x}{100}=x $
$ \Rightarrow $ $ \frac{105x}{100}-x=1500 $
$ \Rightarrow $ $ \frac{5x}{100}=1500 $
$ \Rightarrow $ $ x=30000 $
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Concepts Used:
Sets
Set is the collection of well defined objects. Sets are represented by capital letters, eg. A={}. Sets are composed of elements which could be numbers, letters, shapes, etc.
Example of set: Set of vowels A={a,e,i,o,u}
Representation of Sets
There are three basic notation or representation of sets are as follows:
Statement Form: The statement representation describes a statement to show what are the elements of a set.
- For example, Set A is the list of the first five odd numbers.
Roster Form: The form in which elements are listed in set. Elements in the set is seperatrd by comma and enclosed within the curly braces.
- For example represent the set of vowels in roster form.
A={a,e,i,o,u}
Set Builder Form:
- The set builder representation has a certain rule or a statement that specifically describes the common feature of all the elements of a set.
- The set builder form uses a vertical bar in its representation, with a text describing the character of the elements of the set.
- For example, A = { k | k is an even number, k ≤ 20}. The statement says, all the elements of set A are even numbers that are less than or equal to 20.
- Sometimes a ":" is used in the place of the "|".