# math

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1. Find the LCD of 3/5 and 1/6.

a. 5
b. 6
c. 11
d. 30

2/5 + 1/9

a. 1/15
b. 23/45
c. 3/14
d. 19/45

4/5 - 3/8

a. 1/40
b. 1 7/40
c. 7/10
d. 17/40

4. If Sandy's cookie recipe calls for 1/3 cup of brown sugar and she increases it by 2/9 of a cup, how much brown sugar does she have?

a. 7/9 cup
b. 5/9 cup
c. 4/9 cup
d. 1/9 cup

5/8 - 1/6

a. 30/48
b. 19/24
c. 6/8
d. 6/6

• math - ,

I'll show you the first two.

1. Find the LCD of 3/5 and 1/6.

a. 5
b. 6
c. 11
d. 30

The LCD is the smallest number divisible by both denominators.
Let's look at the multiples of 6:
6, 12, 18, 24, 30. The only one of those numbers that's also divisible by 5 is 30.

2/5 + 1/9

a. 1/15
b. 23/45
c. 3/14
d. 19/45

The least common denominator must be 45.
2/5 = 18/45
1/9 = 5/45

• math - ,

here they are
3. a
4. b
5. c

if they r wrong plz tell me the right ones

• math - ,

help any body

• math - ,

3 is wrong.
4 is right.

I don't think the correct answer is one of your choices for 5.

My answer for 5 is 11/24.

Please make sure you've copied the problem correctly.

• math - ,

3. 4/5 - 3/8
the LCD is 40, but you can't just subtract the numerators. "fifths" and "eighths" aren't the came kind of things. In order to make them both into "fortieths" you have to make the denominators equal to 40.

The key to this kind of pronblem is to remember that multiplying by 1 does not change anything. to make 5 into 40, you need to multiply by 8. But to avoid changing the value, you multiply by 8/8 which is just 1.

4/5 * 8/8 = 32/40
3/8 * 5/5 = 15/40

Now everything is expressed in "fortieths", so you can now just subtract. 32-15 = 17, so

4/5 - 3/8 = 32/40 - 15/40 = 17/40
-------------------------
4. 1/3 + 2/9

1/3 * 3/3 = 3/9

3/9 + 2/9 = 5/9
5. 5/8 - 1/6

5/8 * 3/3 = 15/24
1/6 * 4/4 = 4/24

15/24 - 4/24 = 11/24
Hmmm. Not given
However, 5/8 + 1/6 = 19/24. Typo?

• math - ,

1.d 30
2.c 5/14
3.b. 5/9
4.d 8/15
5. a 1 1/2, 1 1/9