Decimal Numbers

Question 0

How do you add decimal numbers?

Ex:1.5+2.9

Answer 0

Decimal numbers are added just like whole numbers, the only change is that the decimal point must be after the same number of digits as the numbers.
Ex:               1.5
               \+   2.9
               \_\_\_\_\_\_
                    4.4
LOOK OUT! Do NOT do this:
                1.5
          \+ 2.6 7
           \_\_\_\_\_\_
             2.8 2
THIS is what you must do:
               1.5
          \+   2.67
          \_\_\_\_\_\_\_
               4.17

Question 1

Define a decimal number:

Answer 1

A decimal number is a number that is not completely whole.
Ex:0,5
Sometimes the number is equivalent to a fraction.
Ex:0.5=1/2
There can be several digits after the decimal point.
Ex:1.36
2.167
In some countries, there is a comma instead of a decimal point.
Ex:1,36
2,167

Question 2

a) What is the second digit’s place in the decimal 2.5 called?
b) What is the first digit’s place in the decimal 23.7 called?

Answer 2

a) It is the tenths position.

b) It is in the tens position.

Question 3

a) What is the third digit’s place in the decimal 1.74 called?
b) What is the first digit’s place in the decimal 254.67 called?

Answer 3

a) It is in the hundredths position.

b) It is in the hundreds position.

Question 4

How do you multiply two decimal numbers?

Ex:1.5x1.5

Answer 4

You multiply them like you would with whole numbers, with a few changes.
Ex: 1.5 Imagine taking away the decimal point.
X 1.5 There are 2 digits after the decimal point in all.
_______
75
+ 170
_______
245 Now we put back two digits after the decimal
point.
2.45

Question 5

3.6+4.5=?

Answer 5

8.1

Question 6

7.2-3.8=?

Answer 6

3.4

Question 7

3.5x5=?

Answer 7

1.75

Question 8

16.86:2=?

Answer 8

8.43

Question 9

9.6:3=?

Answer 9

3.2

Question 10

Which is the biggest?

• 0.1
• 0.10
• 0.100
• 0.1000

Answer 10

They are all the same. All numbers are decimal, actually.
Ex:5=5.0=5.00
Whole numbers are all the decimal numbers that only have zeroes after the decimal point, but since they mean there is nothing after the decimal point, we just don’t bother to put them.
Decimal numbers also have zeroes after their digits.
Ex:2.56=2.560
Sometimes it helps for division and substraction.
Ex:5.6-2.34=5.60-2.34

Question 11

Give a decimal number between 1.5 and 1.7

Answer 11

Any number is good, as long as it is bigger than 1.5 and smaller than 1.7
Ex:1.51;1.52;1.53;1.54…
1.511;1.512;1.513…
LOOK OUT! 1.61 is not bigger than 1.7!
ALWAYS look at the first digit, and if it’s the same, look at the second…

Question 12

Give the fraction equivalent of 2.5:0.5

Answer 12

IMPORTANT!
NEVER use a decimal number for a fraction.
You cannot do 2.5/0.5
You must do 5/1
Plus, usually it's much simpler.