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Success step english 4 pdf
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Mô tả chi tiết
13
5
7
− 6
6
7
1. Notice the common denominator
of the fractions: 7
2. Add that number to the numerator
of the top fraction: 5 + 7 = 12
3. Subtract one from the top integer: 13 − 1 = 12
4. Subtract as usual: 12
1
7
2
−6
6
7
6
6
7
Multiplying and Dividing Fractions
When multiplying fractions, simply multiply the
numerators and then multiply the denominators:
5
6
×
7
8
=
3
4
5
8
When dividing, turn the second fraction upsidedown, then multiply across:
1
2
÷
2
3
is the same as
1
2
×
3
2
=
3
4
When working with problems that involve mixed
numbers such as 6
1
2
× 5
1
3
, change the numbers to
improper fractions before multiplying. With 6
1
2
,
multiply the denominator, 2, by the whole number, 6,
to get 12, then add the numerator, 1, for a total of 13.
Place 13 over the original denominator, 2. The result is
1
2
3
.
When multiplying or dividing a fraction and an
integer, place the integer over 1 and proceed as if it
were a fraction.
13 ×
1
2
=
1
1
3
×
1
2
=
1
2
3
= 6
1
2
Choosing an Answer
When you come up with an answer where the numerator is more than the denominator, the answer may be
given in that form, as an improper fraction. But if the
answers are mixed numbers, divide the denominator
into the numerator. Any remainder is placed over the
original denominator. In the case of
20
6
8
, 208 divided
by 6 is 34 with a remainder of 4 yielding 34
4
6
. This
answer probably will not be there, so reduce
4
6
to
2
3
. If
20
6
8
is not an answer choice, 34
2
3
probably will be. But
don’t worry about having to choose between these two
answers. Since they signify the same amount, the test
would not be valid if both
20
6
8
and 34
2
3
were there
unless the question specifically asked for a fully
reduced answer.
HOT TIP
When you’re working with two fractions where the
numerator of one fraction can be divided by the same
number as the denominator of the other fraction, you can
reduce even before you multiply:
6
1
2
× 5
1
3
=
1
2
3
×
1
3
6
Divide both the 2 and the 16 by 2: HOT TIP
When adding or subtracting fractions, you can use the
laser beam method.
1. First change to improper fractions, then multiply
crosswise:
2. Next, multiply the denominators: 6 × 7 = 42
3. Add or subtract the top numbers as appropriate and
place them over the multiplied denominator to get your
answer: 7 + 18 = 25
2
4
5
2
–CBEST MINI-COURSE–
103
1
6
3
7
7 18 1
6
3
7 + =
13
2
16
3
104
3
2
3 × = = 1
8 34