Ex.3.1 Q8 Data Handling - NCERT Maths Class 7

Go back to  'Ex.3.1'

Question

 The rainfall (in mm) in a city on \(7\) days of a certain week as recorded as follows:

Day

Mon

Tue

Wed

Thurs

Fri

Sat

Sun

Rain fall (in \(\rm mm\))

\(0.0\)

\(12.2\)

\(2.1\)

\(0.0\)

\(20.5\)

\(5.5\)

\(1.0\)

(i) Find the range of the rainfall in the above data.

(ii) Find the mean rainfall of the week.

(iii) On how many days was the rainfall less than the mean rainfall?

Text Solution

What is known?

Rainfall in \(\rm mm\)

What is unknown?

Range of the rainfall and mean rainfall

Reasoning:\(\begin{align}\text{Mean of the rainfall }\left( \text{in mm} \right)=\frac{\text{sum of rain falls( in mm) }}{\text{Number of days}}\end{align}\)

Steps:

(i)Highest of the rainfall (in \(\rm m\rm m\)) \(= 20.5\)

Lowest of the rainfall (in \(\rm m\rm m\)) \(= 0.0\)

Range of the rainfall = Highest rainfall – Lowest rainfall

\(= 20.5 – 0.0\)

\(= 20. 5 \rm\,mm\)

(ii)Total number of days \(= 7\)

Record of the rainfall (in \(\rm mm\)) \(= 0.0, 12.2, 2.1, 0.0, 20.5, 5.5, 1.0\)

\[\begin{align}{\text{Mean of the rainfall }}\left( {{\text{in mm}}} \right) &= \frac{{0.0 + 12.2 + 2.1 + 0.0 + 20.5 + 5.5 +1.0}}{7}\\ &= \frac{{41.3}}{7}\\ &= 5.9\end{align}\]

(iii)On \(5\) days rainfall was less than the mean rainfall i.e., Monday, Wednesday, Thursday, Saturday and Sunday.

  
Learn from the best math teachers and top your exams

  • Live one on one classroom and doubt clearing
  • Practice worksheets in and after class for conceptual clarity
  • Personalized curriculum to keep up with school