## STAM 102 :: Lecture 09 :: Use of in-built functions and writing expressions # In-built Functions

• A function is an in-built program, which is used to do a particular task.
• Functions take the input the input and will give the result as the output.
• Based on the input and output data the functions are categorized as
• String functions
• Arithmetic functions
• Date functions
• Logical functions
• Group functions

Use of in-built function SUM()
To use in-built functions enter the data to prepare mark list of the I- B.Sc.(Agriculture) students in the spreadsheet. • Using the in-built function SUM() we can calculate the total scored by each and every student in I-B. Sc. (Agri.). • Place the mouse pointer in the cell with the address F3
• The F3 cell is the one which should display the total mark scored by the student namely Angaleeswari in the above example.
• Click on Insert Menu à Function
• or Select fx in the Formula bar
• Insert Function dialog box will get displayed as shown below: • Select SUM function and click OK button in the Insert Function dialog box.
• The function Argument dialog box will be displayed with the automatically assumed range of cells to be added(B3 to E3) • Click OK. The result is displayed as shown. We can even choose the range of cells added manually. • The total marks scored by the other students have to added in the same way by making use of the SUM() function.
• Instead entering the same function for all the students in the example we can copy the formula to the cells in the total column to add B4:E4, B5:E5, B6:E6 and so on.
• When we copy the SUM() function formula from the cell F3 to F4 the SUM function will automatically taking the input range of numbers to be added is B4:E4.
• The same is applicable to the rest of the cells in the total column.
• To copy down the formula place the mouse pointer at the bottom right corner of the cell F3.
• The mouse pointer now automatically changes into + symbol.
• Now drag + symbol down the cells in the Total column.
• We can see the total marks of all the students in the example as shown below. Use of in-built function AVERAGE()

• To calculate the average marks scored by the students in the example we can make use of average function AVERAGE().
• Enter Average column in the spreadsheet.
• Place the mouse pointer in the cell with the address G3
• The F3 cell is the one which should display the total mark scored by the student namely Angaleeswari in the above example.
• Click on Insert Menu à Function
• or Select fx in the Formula bar
• Insert Function dialog box will get displayed as shown below. Choose AVERAGE() function and click OK. • Click OK button in the Insert Function dialog box.
• In the Function Argument dialog box enter F3/4  then click OK button. The average scored is displayed. • Copy the AVERAGE formula as we copied the SUM(). # Writing Expressions

• The total marks can be calculated by writing expressions.
• Place the cursor the cell F3.
• To enter expression, enter the equal sign first. • Choose the cells with the cursor as sown • Press enter. The result will be displayed in F3. Copy the expression down the Total column to find the total mark scored by all the students in the example.
• To calculate the averages place the G3.
• Enter the equal sign first in the cell G3.
• Enter F3/4 which is the average to be calculated. • Press enter. The average will be displayed. Copy the expression down the cells in the Average column to calculate the rest of the averages.  Download this lecture as PDF here
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