Power

Most calculators get their power from a solar cell. This powers the calculator so long as light is available (daylight, electric bulb or even candle-light).

Display

The display shows the answers. The digits in the display are usually made of small line segments.

Keyboard

The keyboard has four main set of keys or buttons:

1. Number keys

Press these keys: “0”, “1”, “2”, “3”, “4”, “5”, “6” ,”7” , “8”, “9” and the decimal point key (usually shown as a dot .) to enter number into the calculator.

2. Basic calculation keys

Press these keys: “+”,” –“, “X”, “÷”, “%”, “√” and “=” to operate on the numbers you have entered, and to display answers.

3. Clearing keys

The “c” key clears the last number you entered. Press “c” if you entered a wrong number by mistake. On some calculator “CE” is written instead of “C”. The “AC” key clears the whole calculation that you are working on. Use this if you want to start from the beginning again. Often the “AC” key is linked to the calculator’s ON key and is written as “ON/AC” or just as “AC”. Press “AC” before starting any calculation and 0 is shown on the display.

4. Memory keys
5. Memory plus key

Press M+ to store the displayed number in the memory of the calculator. If there is any previous number in the number, it adds the displayed number to it.

1. Memory minus key

Press “M -“ to subtract the displayed number from the number in the. The answer obtained from the addition or subtraction will be the new number in the memory.

1. Memory recall key

If there is a number in the memory, the calculator usually shows a small M in the corner of the display.

Press “MR” to display the number in the memory.

1. Memory clear key

Press “MC” to clear the number stored in the memory.

Exercise

1. Display on your calculator:
2. The highest possible number,
3. the lowest possible number.
4. To find what a snail lives in:
5. calculate 5 X 31 X 499;
6. turn your calculator upside down and read the display.
7. Use your calculator to complete the table below

1. Look at the final digits of the values displayed in the table above. Is there a pattern? If so, what is it?
2. Is there a recognizable pattern in the final two digits?

Using Tables

If calculators are not available, then calculations can be done by using tables such as the one below.

Table of squares can be used to convert 2-digit numbers to squares of those numbers.

Tables of squares and square roots (Squares from 1.0 to 9.9).

Approximate Square roots

5² = 5 X 5 = 25

Thus √25 = 5.

Numbers that have exact square roots are said to be perfect square.  We can find the approximate square root of a number by knowing the perfect squares immediately before and after it.

Example

Between what whole numbers do the square roots of the following numbers lie?

3. 3.6 b. 9.4 c. 40 d. 78

Solution

3. √3.6

3.6 lies between    1 and   4

thus √3.6 lies between √1 and √4

i.e.     √3.6 lies between     1 and   2

9. √9.4

9.4 lies between    9 and    16

thus √9.4 lies between √9 and √16

i.e.    √9.4 lies between    3 and    4

1. √40

40 lies between    36 and   49

Thus √40 lies between √36 and √49

i.e.        40 lies between       6 and    7

1. √78

78 lies between     64 and    81

Thus √78 lies between  √64 and √81

i.e.      √78 lies between     8 and      9

Exercise

1. Find the valueof the following
2. 1.4² b. 2.3² c. 6.8² d. 7.2² e. 4.9² f. 8.5²