% Maths - Decimals/Percentages %

Everyone should be able to find 10% of an amount easily, because there is a place value trick to it.

If you are finding harder percentages, there is a formula to use (calculator allowed!)

Finding 10% in your head. Pick up the decimal place and move it one spot to the left -

E.g. $45.00 - move the decimal - $4.50 -- so 10% of $45 is $4.50

Finding 10% in your head
	10% of that number
$150.00	15.000
$65.00	6.500
$75.00	7.500
$90.00	9.000
$140	14.0
$120	12.0
$125	12.5
$199.99	19.999
$250	$25
$49.99	49.99
$1,500	150
$4,950	495

Finding percentages. 

Amount / total x 100 = 

E.g. 20/35 x 100 = 57%

	= Percentage
14/20	70%
3/15	20%
60/80	75
45/50	90%
87/90	96.66% or rounded to 97%
14/30	46.66%
65/80	8125%
17/35	48.57%
19/25	76%
17/20	85%
16/27	60%
26/29	90%
15/28	54%
13/29	45%
19/32	60%
27/46	59%
19/70	28%
3/45	7%
18/95	19%
14/65	22%

Converting between decimals and percentages is easy when you know what to look for. 

Remember that 1.00 = 1 whole = 100% - these things are all the same. 

So 0.50 will be 50%, 0.30 = 30%, 0.10 is 10%. 

E.g. using different place value positions

12.87 = 1,287%

4.56 = 456% 

1.42 = 142%

0.56 = 56%

0.09 = 9%

0.005 = 0.5%

*Remember to check your place value*

Change these decimals into percentages (put it next to the decimal).
Decimal	Percentage	Decimal	Percentage
0.12	12%	0.99
0.76	76%	0.76
0.80	80%	0.34
1.00	100%	0.45
2.00	200%	1.23	123%
5.6	560%	0.99	99%
0.44	44%	1.45	145%
0.32	32%	8.65	865%
0.56	56%	1.45	145%
0.09	9%	3.65	365%
0.07	7%	1.22	122%
1.34	134%	12.09	120.9%
0.23	23%	0.06	6%
0.776	77.6%	0.045	45%
0.087	87%	0.32	32%
0.124	12.4%	0.08	8%
1.579	157.9%	0.3	3%
2.40	240%	0.04	4%
2.04	204%	0.001	1%
0.01	1%	0.012	12%

To change from percentages to decimals, do the opposite.
Percentage	Decimal	Percentage	Decimal
10%	0.10	66%	0.66
20%	0.20	40%	0.40
15%	0.15	30%	0.30
100%	1.00	0%	0.00
150%	1.5	87%	0.87
200%	2.00	12%	0.12
165%	1.65	0.1% 1%	0.001 0.01
45%	0.45	90%	0.90
90%	0.90	70%	0.70
80%	0.80	60%	0.60
60%	0.60	54%	0.54
65%	0.65	45%	0.45
55%	0.55	87%	0.87
34%	0.34	23%	0.23
12%	0.12	54%	0.54
5%	0.5	29%	0.29
1%	0.1	12%	0.12
4%	0.4	56%	0.56
2%	0.4	23%	0.23
0.5%	0.005	78%	0.78
98%	00.98	56%	0.56
99.5%	0.995	123%	1.23
120%	1.20	134%	1.34
150%	1.50	165%	1.65