Measurements of the diameters, in centimeters, in centimeters, of 20 copper spheres are distributed as...

JAMB 1984

Measurements of the diameters, in centimeters, in centimeters, of 20 copper spheres are distributed as shown below
\(\begin{array}{c|c} \text{Class boundary in cm} & \text{frequency} & \\\hline 3.35 - 3.45 & 3\\ 3.45 - 3.55 & 6\\ 3.55 - 3.65 & 7\\ 3.65 - 3.75 & 4\end{array}\)
What is the mean diameter of the copper spheres?

A. 3.40cm
B. 3.58cm
C. 3.56cm
D. 3.62cm

WAEC and NECO CBT Software for Computers and Laptops - Candidates, Schools, Centres, Resellers - 100% Offline -Download Now

Your School's Whatsapp Group - Join Us now

WAEC and NECO CBT App for Mobile Devices - Candidates, Schools, Centres, Resellers - 100% Offline -Download Now

Correct Answer: Option C

Explanation

\(\begin{array}{c|c} \text{x(mid point)} & f & fx\\ \hline 3.4 & 3 & 10.2 \\ 3.5 & 6 & 21.0\\3.6 & 7 & 25.2\\3.7 & 4 & 14.8\end{array}\)

\(\sum f\) = 20

\(\sum fx\) = 71.2

mean = \(\frac{\sum fx}{\sum f}\)

= \(\frac{71.2}{20}\)

= 3.56

Previous Next

Go back to Maths classroom

Report an Error Ask A Question Download App