Help with some homework.

13. What is 3.56 x 10^-5 in standard form?
14. Which of the following appears to be an irrational number?
15. Which number is equivalent to 0.454545?
16. Riding the bus, Roger uses 1/3 of his money for bus fare. What is the fraction of his money expressed as a decimal?
17. Josh has 5/8 of a foot of plywood. To finish building the deck, he needs five times that amount. How many feet of plywood does Josh need?
18. -1/6 + (-3/7)=
19. 11/12 + (-2 /3)=
20. 10 5/18 - 8 5/6
21. 1/4 x -1/2
I'm super desperate, I have until midnight.

6 answers

If you’re expecting someone to hand you the answers, you’ve come to the wrong website. But if you actually want help, a math tutor might give up part of New Year’s Eve. No guarantees, though.
I understand, I'm just trying to get this done so I dont fail this semester and get kicked out of school. Sorry.
Here’s something you can do now. Go to https://www.mathsisfun.com/ and click on Numbers. Then go into the Fractions menu, and you should find explanations and examples for some of your questions.
Thank you so much. I really appreciate this.
You’re welcome.

There’s an Algebra section there, too, which you might find helpful.
#13: move the decimal place 5 to the left, filling in zeroes as needed
#14: ???
#15: when you have a group of repeating digits, place them over an equal number of nines. Thus
0.454545... = 45/99 = 5/11
Of course, you may have to adjust if there are leading non-repeating digits.
0.004545 = 0.01 * 0.454545 = 1/100 * 5/11 = 5/1100 = 1/220
0.23454545 = 0.23 + 0.00454545 = 23/100 + 1/220 = 129/550

#16: just do the division ... 1/3 = 0.3333...
#17: 5 * 5/8 = 25/8 = 3 1/8
#18: -1/6 + (-3/7) = -1/6 - 3/7 = -7/42 - 18/42 = -25/42
#19: 11/12 + (-2 /3) = 11/12 - 8/12 = 3/12 = 1/4
#20: 10 5/18 - 8 5/6 = 9 23/18 - 8 15/18 = 1 8/18 = 1 4/9
#21: 1/4 x -1/2 = -(1/4)(1/2) = -1/8
when multiplying fractions, multiply the tops and bottom, then simplify.
2/3 * 3/8 = 6/24 = 1/4
when dividing, multiply by the reciprocal of the divisor.
2/3 ÷ 3/8 = 2/3 * 8/3 = 16/9

If any of this is still unclear, you have some studying to do, yeah?