# Math Help - prime or composite

1. ## prime or composite

hello everyone i have a math review and i want the RIGHT answers so i can check my work. And so I know that I'm doing each problem right thanks.

#1. Is the number 75 prime,composite, or neither? (i say composite?)
#2. Is the number 37 prime,composite, or neither? (i say prime?)
#3. Is the number 1 prime,composite, or neither? (i say neither?)
#4. Is the number 42 prime,composite, or neither? (i say composite?)

Perform the indicated operation.
#5. 15/18 x 12/5 (i say its 2?)
#6. 3 4/7 x 2 1/5 (i say its 55/7?)
#7. 1 4/11 divide 3 (i dont know?)
#8. 5/8 divide 2 1/3 (i dont know?)
#9. 3 1/3+4 7/8+2 5/6 (i dont know?)
#10. 4/7+3/7+2 1/4 ( i say 3 1/4?)
#11. 5/9-1/3 ( i say 16/27?)
#12. 5 7/8-3 1/2 ( i say 2 3/8?)

#13. A utility stock listed at 18 7/8 on Wednesday rose 2 1/2 points on Thursday and dropped 1 5/8 on Friday. What was it worth when the market closed on Friday? (i say 19 3/4?)

#14. Marco added 3 3/4 cup of water to a bowl. He then decided that was too much, so he took a 1/4 cup measuring cup and dipped it into the bowl three times, taking out the water each time, full to the top of the measuring cup. How much was left in the bowl? ( i say 3 cups?)

#15. Write 8.064 as a fraction. Do not write in lowest terms.
#16. Write 0.0345 as a fraction. Do not write in lowest terms.

Perform the indicated operation(s).
#21.(0.00239x10000) divide 1.5
#22. 4501.2 x 0.003
#23. write 7.8% as a decimal.
#24. write 82.3% as a decimal.
#25. write 2 3/8 as a decimal.
#26. write 15 2/3 as a decimal.
#27. write 3.45 as a percent.
#28. write .012 as a percent.
If anyone knows this stuff let me have it to check my answers because i dont want to flunk. thank you...

2. Originally Posted by abb1327
hello everyone i have a math review and i want the RIGHT answers so i can check my work. And so I know that I'm doing each problem right thanks.

#1. Is the number 75 prime,composite, or neither? (i say composite?) Correct
#2. Is the number 37 prime,composite, or neither? (i say prime?) Correct
#3. Is the number 1 prime,composite, or neither? (i say neither?) Correct
#4. Is the number 42 prime,composite, or neither? (i say composite?) Correct

Perform the indicated operation.
#5. 15/18 x 12/5 (i say its 2?) Correct
#6. 3 4/7 x 2 1/5 (i say its 55/7?) Correct
#7. 1 4/11 divide 3 (i dont know?) See below
#8. 5/8 divide 2 1/3 (i dont know?) See below
#9. 3 1/3+4 7/8+2 5/6 (i dont know?) See below
#10. 4/7+3/7+2 1/4 ( i say 3 1/4?) Correct
#11. 5/9-1/3 ( i say 16/27?) See below
#12. 5 7/8-3 1/2 ( i say 2 3/8?) Correct

#13. A utility stock listed at 18 7/8 on Wednesday rose 2 1/2 points on Thursday and dropped 1 5/8 on Friday. What was it worth when the market closed on Friday? (i say 19 3/4?)

#14. Marco added 3 3/4 cup of water to a bowl. He then decided that was too much, so he took a 1/4 cup measuring cup and dipped it into the bowl three times, taking out the water each time, full to the top of the measuring cup. How much was left in the bowl? ( i say 3 cups?)

#15. Write 8.064 as a fraction. Do not write in lowest terms.
#16. Write 0.0345 as a fraction. Do not write in lowest terms.

Perform the indicated operation(s).
#21.(0.00239x10000) divide 1.5
#22. 4501.2 x 0.003
#23. write 7.8% as a decimal.
#24. write 82.3% as a decimal.
#25. write 2 3/8 as a decimal.
#26. write 15 2/3 as a decimal.
#27. write 3.45 as a percent.
#28. write .012 as a percent.
If anyone knows this stuff let me have it to check my answers because i dont want to flunk. thank you...
#7) $3\div1\frac{4}{11}$ or is it $1\frac{4}{11}\div 3$?

1st way: $\frac{3}{1}\div1\frac{4}{11}=\frac{3}{1}\div\frac{ 15}{11}=\frac{3}{1}\times\frac{11}{15}=\frac{33}{1 5}=\frac{11}{5}=2\frac{1}{5}$

2nd way: $1\frac{4}{11}\div 3=\frac{15}{11}\times\frac{1}{3}=\frac{15}{33}=\fr ac{5}{11}$

#8) $\frac{5}{8}\div2\frac{1}{3}$ or is it $2\frac{1}{3}\div \frac{5}{8}$?

You should be able to do this one looking at #7 as a guide.

#9) $3\frac{1}{3}+4\frac{7}{8}+2\frac{5}{6}$

Change mixed numbers to improper fractions.

$\frac{10}{3}+\frac{39}{8}+\frac{17}{6}$

Find common denominator = 24 and convert each denominator to 24.

$\frac{80}{24}+\frac{117}{24}+\frac{68}{24}$

Add numerators $\frac{80+117+68}{24}=\frac{265}{24}$

#11) $\frac{5}{9}-\frac{1}{3}=\frac{5}{9}-\frac{3}{9}=\frac{2}{9}$

3. Originally Posted by abb1327
If anyone knows this stuff let me have it to check my answers
I have a better plan. You SHOW YOUR WORK and someone will be glad to point out where you wander off if you do.

Originally Posted by abb1327
#1. Is the number 75 prime,composite, or neither? (i say composite?)
This is NOT showing your work. WHY do you think it is "composite"?
Originally Posted by abb1327
#5. 15/18 x 12/5 (i say its 2?)
This is NOT showing your work. Here's an example of showing your work.

15/18 * 12/5

Muliply numerators and denominators

(15*12)/(18*5) = 180/90 = 18/9 = 2

Hey, wait a minute, can I simplfy as I go by using the commutative property and associative property?

$\frac{15}{18}*\frac{12}{5} = \frac{5}{6}*\frac{12}{5} = \frac{5}{5}*\frac{12}{6} = 1*2 = 2$

4. Originally Posted by abb1327

#13. A utility stock listed at 18 7/8 on Wednesday rose 2 1/2 points on Thursday and dropped 1 5/8 on Friday. What was it worth when the market closed on Friday? (i say 19 3/4?) Correct

#14. Marco added 3 3/4 cup of water to a bowl. He then decided that was too much, so he took a 1/4 cup measuring cup and dipped it into the bowl three times, taking out the water each time, full to the top of the measuring cup. How much was left in the bowl? ( i say 3 cups?) Correct

#15. Write 8.064 as a fraction. Do not write in lowest terms.
3 decimal places indicate thousandths, so $8.064=8\frac{64}{1000}=\frac{8064}{1000}$

#16. Write 0.0345 as a fraction. Do not write in lowest terms.

4 decimal places mean ten-thousandths. so $0.0345=\frac{345}{10000}$

Perform the indicated operation(s).
#21.(0.00239x10000) divide 1.5

Multiply by 10000 by moving the decimal 4 places to the right. Then divide by 1.5. $23.9\div1.5=15.9\overline{3}=\frac{239}{15}$

#22. 4501.2 x 0.003

Simple multiplication. Are you allowed to use a calculator? The product should have 4 decimal places. Try it.

To do these, simply remove the % sign and move the decimal 2 places to the left.

#23. write 7.8% as a decimal.

7.8% = .078

#24. write 82.3% as a decimal.
#25. write 2 3/8 as a decimal.
#26. write 15 2/3 as a decimal.
#27. write 3.45 as a percent.

To do this one, move the decimal 2 places to the right and attach a % sign.
#28. write .012 as a percent.

.012 = 1.2%

If anyone knows this stuff let me have it to check my answers because i dont want to flunk. thank you...
Most of the answers above are in Red. Three words of advice: Practice, Practice, Practice

5. ## hey thanks

hey i have one question? On # 21. i really didnt understand how you did that? because i was taught to times them together and then just normaly divide them. But i really didnt undersatnd your work.?
But you did help me alot on them but on number 11. also i thought you were supposed to times both sides by the opposite denominator and i see that you only times the second fraction. That really confused me. But other wise you really did help me and i thank you. keep up the great work. thanks.

6. Show your work. Display your intermediate results. It will be easy to see where you wandered off.

7. Originally Posted by abb1327
hey i have one question? On # 21. i really didnt understand how you did that? because i was taught to times them together and then just normaly divide them. But i really didnt undersatnd your work.?
But you did help me alot on them but on number 11. also i thought you were supposed to times both sides by the opposite denominator and i see that you only times the second fraction. That really confused me. But other wise you really did help me and i thank you. keep up the great work. thanks.
#21 looks like first you multiply, then you divide. I'm not sure about your wording. When you say "divide", are you really saying "divide by"? I assumed you were dividing the product of ((0.00239x10000) by 1.5 and that's what I did. If you meant it the other way around, it would be $1.5\div(0.00239\times10000)=1.5\div23.9=\frac{15}{ 239}$

#11 looks like a subtraction problem to me. Did I miss something? All I did was make sure I had a common denominator of 9 for the two fractions. Then, I subtracted the numerators.

$\frac{5}{9}$ requires us to do nothing.

$\frac{1}{3}$ must be changed to $\frac{3}{9}$

$\frac{5}{9}-\frac{3}{9}=\frac{5-3}{9}=\frac{2}{9}$

You're welcome.

8. #22. 4501.2 x 0.003

Simple multiplication. Are you allowed to use a calculator? The product should have 4 decimal places. Try it.
4501.2X.003=13,503.6 or .60 or .600 or.600000 in other words 1 decimal point
or a million.

BTW, if a number is not prime it is composite. 1 may be considered prime or may be considered neither prime nor composite.