I need HELP!Who's a LIFE SAVER HERE?!?

Question

Well, I have 4 questions that I need help on.It's for Algebra 3-4.I did the rest BUT i need only 4 and they are Brain TEASER puzzles.Help my by solving them.If you don't know at least help me on one of them and i will be happy.Thank you!And If you help me find all of them then I will mark you as best answer.I PROMISE!But it has to be near to being right.Thank you Life savers!Oh yeah it's DUE soon!So help please!

1.How many ways can change be made for 50 cents, using quarters, dimes, nickels and pennies?

2.A merchant set the selling price of a shirt 40% above what it costs him. Then seeing that it did not sell, he decided to reduce the figure by 15%. The final price was $8.65. What did the shirt cost the merchant?

3.How many times between 3 am and 3 pm will the hands of a clock cross?

4.If there were 20 students at a picnic and they all shake hands with each other, how many handshakes are made?

Oh sorry BUT can you plz show me how did you get that answer.Cuz we need to show our work and how did we got it.Sorry for this late NOTE!

I need only question #1...
I need life savers here!
Oh yeah give me how did you got that #...
Show me the work plz!

Answer 1

1.) 13+12+11+...1 = 91
91 different ways

2.) 85% of 140% of x = $8.65
0.85(1.40x) = 8.65
1.19x = 8.65
x = $7.27

3.) 1 time/hr - 12hrs*1 = 12
12 times

4.) 19+18+17+...1 = 190
190 handshakes

Answer 2

1) Two quarters; one quarter, two dimes, one nickel; one quarter one dime, three nickels; five dimes; four dimes, two nickels; three dimes, four nickels; two dimes, six nickels; one dime, eight nickels; ten nickels. That's nine ways without any pennies. You can take it from there, if you're willing to do the work.

2) Let C be the original cost. The first selling price would be C + 0.4C (40% is 0.40) or 1.4C. The second selling price would be 85% of the first price (i.e., 100%-15%), so that would be 0.85*1.4C, and that's equal to $8.65. Make that into an equation, do the multiplication on the left, then divide the 8.65 by your answer.

3) They will cross at about 3:16, 4:22, 5:27, 6:33, 7:38, 8:44, 9:49, 10:54, 12 noon, 1:05, and 2:11. That's 11 times. If you have a watch or a clock with hands, you could have figured this out yourself. (To those who think it's 12 times, do this.)

4) Each student will shake hands with 19 others, which is a total of 380 handshakes IF counted separately. However, each of these involves two people, so to avoid counting the shakes twice, just divide 380 by two to get 190 handshakes.

Answer 3

2. (8.65/0.85)/0.6 = 16.96


4. 20*19/2 = 190

Answer 4

1. 16
2. $5.62
3.12
4. 209