Sunday, June 20, 2010

Word Problem in Trignometry

Question:
The wheel of railway carriage is 90 cm in diameter and makes 3 revolutions in a second. How fast is the train moving?

Answer:







=848.6/100 m/sec
=848.6/100000 km/sec
=848.6*3600/100000 km/hr
=30.55 km/hr

Note:
1m = 100cm
1km = 1000m
= (1000)(100)
= 100000 cms

Tuesday, June 15, 2010

Calculation of Standard Devaition and Variance

Calculation of Standard Deviation for Discrete Series.

In the discrete series, when deviations are taken from actual mean, the formula is








Example:

From the following data, compute the value of standard deviations and variance





Suggested answer:
















Standard deviation from assumed mean method:



















=588/40-(52/40)^2
=14.7-1.69
=13.01



Step 1:

If a = assumed mean, then take the deviations of the items from a and call it d

Step 2:

Multiply each deviation by corresponding frequency amd obtain sigma fd

Step 3:

Multiply each fd by the corresponding d to get fd2 and obtain S fd2.

Step 4: