1
BIG 20 STUDY GUIDE
1. 2.6 x 100
2.6 x 100 = 260
To multiply by 10, 100, 1000, etc., use the short cut. Move the decimal:
1 place right for x 10
2 places right for x 100
3 places right for x 1000
Add on zeros when necessary. Drop off front end zeros.
2. 5.1 ÷ 100
5.1 ÷ 100 = 0.051
To divide by 10, 100, 1000, etc., use the short cut. Move the decimal:
1 place left for ÷ 10
2 places left for ÷ 100
3 places left for ÷ 1000
Add on zeros when necessary.
5. 3 = ? decimal
8
To convert a fraction to a decimal, divide the denominator (bottom number)
into the numerator (top number). Keep dividing until you get a zero or a
repeating answer.
6. 0.73 = ? fraction
0.73 = 73 hundredths
= 73 .
100
To convert a decimal number to a fraction, just read the decimal and write as a
fraction.
7. 1 = ? (percent)
2
First convert to a decimal, (as you did in #5) then move the decimal 2 places to
the right and add on a percent sign.
8.
16
9
44
33
4
32
x
x
To do powers with fractions multiply both the numerator and denominator as
many time as indicated by the exponent (power).
9. (1.2)2 1.2
x1.2
24
12 .
1.44
To do powers multiply the number as many times as indicated by the exponent
(power).
10 3% of 820
0.03 x 820 820
x .03
24.60
1. Change the percent to a decimal number by moving the decimal (at
the end) 2 places to the left.
2. Change “of” to x
3. Multiply
11. Round $6.3572 to the nearest cent .
$
63572 636. .
To round a decimal to a decimal to whole number.
1. Circle the place value you are rounding.
2. If the digit to the right is 0,1,2,3, or 4 the circled digit stays the same.
3. If the digit to the right is 5,6,7,8, or 9 add 1 to the circled digit.
12. Round 8 3/7 to the nearest whole
number.
= 8
3/7 is less than half
To round mixed numbers:
1. If the fraction is less than ½, the whole number stays the same.
2. If the fraction is greater than ½, add one to the whole number.
3. 0.06 x 1000
0.06 x 1000 = 60
4. 18.6 ÷ 10
18.6 ÷ 10 = 1.86
0.375
8 )3.000
-2 4
60
56
40
40
0
0.50
2) 1.00
-1 0
0
.50 = 50%
