Question

The diagram shows the histogram of the amount of time spent watching TV in a day for a group of students. Remember that the area of each rectangle is proportional to its frequency. Find the total number of students. (Take the most common base of all rectangles as 1 unit)

• A. $165$
• B. $140$
• C. $130$
• D. $110$

Answer 1

Answer: (B)

$140$

The most common base is $50$, so it is taken as $1$ unit.

For the class $100-200$, the base is $2$ units.

For the class $200-225$ and $225-250$, the base $=\frac{1}{2}$unit
$\therefore$ For the class $100-200$,
The actual frequency $=$ $10\times 2=20$
For the class $200-225$,
The actual frequency $=$ $40\times \frac{1}{2}=20$
For the class $225-250$,
the actual frequency $=$ $30\times \frac{1}{2}=15$
$\therefore$ Total number of students
$=15+25+20+20+15+20+25$
$=140$