Casio Fx82LB Manual

							6  Mastering the calculator using the Casiofx-82LB
You can use the  key but you must press it after the 7.
The key strokes are
The display should read -3.
You could also use the keystrokes 
In this case the calculator recognises the – as a negative (not recommended to do it this way).
3. Multiplication and division
3.1 To multiply numbers
Find the  key (it is shown on the photograph of your calculator here).
key for division key for multiplication 
						

							Mastering the calculator using the Casiofx-82LB  7
Example
To multiply 7 and 3, type
The display should read 21
To find 753 × 492, type
The display should read 370 476
3.2 To divide numbers
Find the  key (it is shown on the photograph of the calculator)
Example
To divide 35 by 7, type
The display should read 5
To divide 7 905 by 85, type
The display should read 93
To divide 56 by 23947 type
The display should read 0.002338497
If it reads 2.3385×10-
03 or something similar, then your calculator is in SCI (Scientific mode). 
See page 2 to change to NORM (normal mode). 
						

							8  Mastering the calculator using the Casiofx-82LB
3.3 Combining multiplication and division
Example
If the question is
 then
it is really 27 ÷ 7 ÷ 4.
Try it.
The display should read 0.964285714
4. Brackets
Find the set of bracket keys on your calculator.
The fx-82 allows you to use many sets of brackets.
Example 
Do the calculation 471 – (93 + 11 + 2) on the calculator. (Make sure your calculation is in 
ordinary comp. mode press 
)
27
74
×------------
LH bracket key
RH bracket key 
						

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The keystrokes required are
The display should read 365. Notice before you press  the display shows 106. This is 
the result of the sum 93 + 11 + 2.
Sometimes in calculations you will see other grouping symbols, for example, { } (called 
braces), [ ] (called square brackets).
Try these examples:
Exercise 1
(a) 25 + (7 + 2 – 4)
(b) 18 (3 + 7) [a multiplication sign is understood 18 × (3 + 7)]
(c) 4 + 5 [2 (3 + 7)] [to use two sets of brackets just press the same button]
(d)
Answers: 30; 180; 104; 1
5
32+ ()----------------- 
						

							10  Mastering the calculator using the Casiofx-82LB
5. Powers
5.1 Squaring and higher powers
62 means 6 × 6. You can use the square key to do this calculation. (It is shown on the 
photograph of your calculator here.)
Press 
the display should read 36.
Or you can use the power key on your calculator.
Find the xy key on your calculator. It should be above the 
Example
To square 6,
that is, find 62, type
The display should read 36
[The first number you put in is the 6. This is the x and the second number you put in (2) is y. 
That is why it is called the xy key.]
power key
square root key 
and square key 
						

							Mastering the calculator using the Casiofx-82LB  11
To find 273 the required key strokes are
and the display should read 19683.
If you have learnt your multiplication tables you will already know the squares of the whole 
numbers from 1 to 12 and thus be able to complete much of the following table.
__________________________________________________________________________
Exercise 2
Use your calculator to find the squares of the whole numbers from 13 to 25 and any other 
squares you are unsure of.
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Exercise 3
You can use this key for other powers as well. Try these examples
(a) 74
(b) 810
(c) (0.4)6 (you do not have to type the brackets in)
(d) (–7)6 (you need to type the brackets in)
(e) 50.4
(f) 5–4
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12 = 1112 =212 =
22 = 4122 =222 =
32 = 9132 =232 = 529
42 =142 =242 = 576
52 =152 =252 = 625
62 =162 =
72 =172 =
82 =182 =
92 =192 =
102202 
						

							12  Mastering the calculator using the Casiofx-82LB
Answers:
(a) 2401
(b) 1073741824
(c) 4.096 × 10–3 or 0.004096 (you move the decimal 3 places to the left)
(d) 117649
(e) 1.903653939
(f) 0.0016 [Just press  5–4 is the same as
 so you could press  to get the same answer]
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5.2 Square Root
Finding the square root of a number ‘undoes’ or ‘neutralises’ the squaring of the number and 
vice versa. The symbol for square root is
 (This is called the radical sign)
The square root of 36 is written as 
Now because 62 = 36, .
Find the square root key on your calculator and type
The display will read 6.
What do you think  is?  = 
__________________________________________________________________________
You should have said 9 because 92 = 81
(Check your calculator)
__________________________________________________________________________
What do you think  will be? You should have said ‘you can’t find the square root of a 
negative’ since you can’t find a number that squares to give a positive. Your calculator will say 
–E–.
1
5
4-----
36
366=
8181
49– 
						

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Exercise 4
Try these by looking at the table of squares you completed on the previous page and then 
check your answers on your calculator
__________________________________________________________________________
The answers are 4, 12, 10, 21, 7, 13, 11, 19.
Let’s now check that taking the square root neutralises squaring.
Try this on your calculator.
Find the square root of 3 squared that is, 
The key strokes required are
The display should read 3
Because squaring and taking square roots are inverse operations, the order of the 
operations can be reversed and the number is unaffected.
So the square, of the square root of 3, should also equal 3
Try it on your calculator. The key strokes required are
__________________________________________________________________________
Exercise 5
Complete the following without using the calculator
(a)=
(b)=
(c)=
(d)=10
(a)  =(e) =
(b)  =(f) =
(c)  =(g) =
(d)  =(h) =
1649
144169
100121
441361
32
72
72
102
2 
						

							14  Mastering the calculator using the Casiofx-82LB
(e)=625
(f)=144
(g)=, because 82=
(h)=, because = 121
(i)=, because =
Check your answers on the calculator.
__________________________________________________________________________
5.3 Other roots
You can also use the root key on the calculator. Find the  on your calculator. To get to 
this key you must press shift first.
Look at the examples below.
Examples
(a) 9½
and the display should read 3.
2
2
64
121
225
root key
shift key 
						

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or
and the display should read 3.
(b)
and the display should read 2.
(c) 16¼
and the display should read 2.
Note: 
Root key is a function at the back of the divide key, so you will need to activate it with the 
SHIFT key
See the key . The x stands for the number and the y stands for the root you want to take.
From the examples above you may have seen that .  is called a fractional 
index.
6. Fractions
How do you add  and ? Normally you would have to find a common denominator of 
252.
So:
8
1
3 ---
x
1
y ---
8
1
3 ---
83=8
1
3 ---
1
12 ------4
63 ------
1
1
2------4
63 ------ +
21
252 ---------
16
252 --------- +
37
252---------==